diff --git a/CMakeLists.txt b/CMakeLists.txt
index eb016dd..78ebf17 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,15 +7,15 @@ set(CMAKE_AUTOMOC ON)
 find_package(Qt6 REQUIRED COMPONENTS Widgets)
 
 qt_add_executable(ImageBrowser
-    main.cpp
-    mainwindow.cpp
-    mainwindow.h
-    imagemodel.cpp
-    imagemodel.h
-    thumbnailworker.cpp
-    thumbnailworker.h
-    imageviewwidget.cpp
-    imageviewwidget.h
+    src/main.cpp
+    src/mainwindow.cpp
+    src/mainwindow.h
+    src/imagemodel.cpp
+    src/imagemodel.h
+    src/thumbnailworker.cpp
+    src/thumbnailworker.h
+    src/imageviewwidget.cpp
+    src/imageviewwidget.h
 )
 
 target_link_libraries(ImageBrowser PRIVATE Qt6::Widgets)
\ No newline at end of file
diff --git a/imagemodel.cpp b/imagemodel.cpp
deleted file mode 100644
index 3288ae0..0000000
--- a/imagemodel.cpp
+++ /dev/null
@@ -1,171 +0,0 @@
-#include "imagemodel.h"
-#include "thumbnailworker.h"
-
-#include <QDir>
-#include <QImageReader>
-#include <QFileInfo>
-#include <QFileIconProvider>
-
-ImageModel::ImageModel(QObject *parent)
-    : QAbstractListModel(parent)
-{
-    m_threadPool.setMaxThreadCount(QThread::idealThreadCount());
-
-    m_placeholder = QPixmap(128, 128);
-    m_placeholder.fill(Qt::lightGray);
-
-    QFileIconProvider iconProvider;
-    m_folderIcon = iconProvider.icon(QFileIconProvider::Folder);
-}
-
-ImageModel::~ImageModel()
-{
-    m_cancelFlag = true;
-    m_threadPool.waitForDone();
-}
-
-void ImageModel::setDirectory(const QString &path)
-{
-    m_cancelFlag = true;
-    m_threadPool.waitForDone();
-    m_cancelFlag = false;
-
-    beginResetModel();
-    m_items.clear();
-    m_pendingRows.clear();
-    m_currentDir = path;
-
-    QDir dir(path);
-
-    // Add subdirectories first
-    dir.setFilter(QDir::AllDirs | QDir::NoDot);
-    dir.setSorting(QDir::Name);
-    const auto dirs = dir.entryInfoList();
-    QPixmap folderPixmap = m_folderIcon.pixmap(128, 128);
-    for (const QFileInfo &d : dirs)
-    {
-        QString name = d.fileName();  // preserves ".." for the parent entry
-        m_items.append({d.absoluteFilePath(), name, folderPixmap, true, true});
-    }
-
-    // Then add image files
-    QStringList filters;
-
-    const auto formats = QImageReader::supportedImageFormats();
-    for (const QByteArray &fmt : formats)
-        filters << "*." + fmt;
-
-    dir.setNameFilters(filters);
-    dir.setFilter(QDir::Files);
-    dir.setSorting(QDir::Name);
-
-    const auto files = dir.entryInfoList();
-
-    for (const QFileInfo &file : files)
-    {
-        m_items.append({file.absoluteFilePath(), file.fileName(), m_placeholder, false, false});
-    }
-
-    endResetModel();
-}
-
-void ImageModel::requestThumbnails(int firstRow, int lastRow)
-{
-    if (m_items.isEmpty())
-        return;
-
-    firstRow = std::max(0, firstRow);
-    lastRow = std::min(lastRow, static_cast<int>(m_items.size()) - 1);
-
-    for (int row = firstRow; row <= lastRow; ++row)
-    {
-        if (!m_items[row].loaded && !m_items[row].isFolder)
-            queueRow(row);
-    }
-
-    // Optional: preload nearby rows
-    int buffer = 20;
-    for (int row = firstRow - buffer; row < firstRow; ++row)
-        if (row >= 0 && !m_items[row].loaded && !m_items[row].isFolder)
-            queueRow(row);
-
-    for (int row = lastRow + 1; row <= lastRow + buffer; ++row)
-        if (row < m_items.size() && !m_items[row].loaded && !m_items[row].isFolder)
-            queueRow(row);
-}
-
-void ImageModel::queueRow(int row)
-{
-    if (m_pendingRows.contains(row))
-        return;
-
-    m_pendingRows.insert(row);
-
-    auto *worker = new ThumbnailWorker(
-        m_items[row].path,
-        row,
-        &m_cancelFlag);
-
-    connect(worker, &ThumbnailWorker::finished,
-            this, &ImageModel::thumbnailReady,
-            Qt::QueuedConnection);
-
-    m_threadPool.start(worker);
-}
-
-QString ImageModel::filePath(const QModelIndex &index) const
-{
-    if (!index.isValid())
-        return {};
-
-    return m_items[index.row()].path;
-}
-
-bool ImageModel::isFolder(const QModelIndex &index) const
-{
-    if (!index.isValid() || index.row() >= m_items.size())
-        return false;
-    return m_items[index.row()].isFolder;
-}
-
-QString ImageModel::currentDirectory() const
-{
-    return m_currentDir;
-}
-
-int ImageModel::rowCount(const QModelIndex &) const
-{
-    return m_items.size();
-}
-
-QVariant ImageModel::data(const QModelIndex &index, int role) const
-{
-    if (!index.isValid())
-        return {};
-
-    const Item &item = m_items[index.row()];
-
-    if (role == Qt::DecorationRole)
-        return item.thumbnail;
-
-    if (role == Qt::DisplayRole)
-        return item.displayName;
-
-    return {};
-}
-
-void ImageModel::thumbnailReady(int row, const QImage &image)
-{
-    if (m_cancelFlag)
-        return;
-
-    if (row < 0 || row >= m_items.size())
-        return;
-
-    m_items[row].thumbnail = QPixmap::fromImage(image);
-    m_items[row].loaded = true;
-    m_pendingRows.remove(row);
-
-    QModelIndex idx = index(row);
-    emit dataChanged(idx, idx, {Qt::DecorationRole});
-}
diff --git a/imagemodel.h b/imagemodel.h
deleted file mode 100644
index 7586159..0000000
--- a/imagemodel.h
+++ /dev/null
@@ -1,53 +0,0 @@
-#pragma once
-
-#include <QAbstractListModel>
-#include <QPixmap>
-#include <QVector>
-#include <QThreadPool>
-#include <QSet>
-#include <atomic>
-#include <QIcon>
-
-class ThumbnailWorker;
-
-class ImageModel : public QAbstractListModel
-{
-    Q_OBJECT
-
-public:
-    explicit ImageModel(QObject *parent = nullptr);
-    ~ImageModel();
-
-    void setDirectory(const QString &path);
-    QString filePath(const QModelIndex &index) const;
-    bool isFolder(const QModelIndex &index) const;
-    QString currentDirectory() const;
-
-    void requestThumbnails(int firstRow, int lastRow);
-
-    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
-    QVariant data(const QModelIndex &index, int role) const override;
-
-    void thumbnailReady(int row, const QImage &image);
-
-private:
-    struct Item
-    {
-        QString path;
-        QString displayName;
-        QPixmap thumbnail;
-        bool loaded = false;
-        bool isFolder = false;
-    };
-
-    void queueRow(int row);
-
-    QVector<Item> m_items;
-    QThreadPool m_threadPool;
-    QPixmap m_placeholder;
-
-    QSet<int> m_pendingRows;
-    std::atomic_bool m_cancelFlag{false};
-    QIcon m_folderIcon;
-    QString m_currentDir;
-};
diff --git a/imageviewwidget.cpp b/imageviewwidget.cpp
deleted file mode 100644
index f09ed6a..0000000
--- a/imageviewwidget.cpp
+++ /dev/null
@@ -1,237 +0,0 @@
-#include "imageviewwidget.h"
-
-#include <QPainter>
-#include <QKeyEvent>
-#include <QMouseEvent>
-#include <QImageReader>
-#include <algorithm>
-
-ImageViewWidget::ImageViewWidget(QWidget *parent)
-    : QWidget(parent)
-{
-    setFocusPolicy(Qt::StrongFocus);
-    setStyleSheet("background-color: black;");
-}
-
-void ImageViewWidget::setImage(const QString &path)
-{
-    QImageReader reader(path);
-    reader.setAutoTransform(true);
-    QImage image = reader.read();
-
-    if (!image.isNull())
-        m_pixmap = QPixmap::fromImage(image);
-    else
-        m_pixmap = QPixmap();
-
-    m_zoomMode = FitToScreen;
-    m_zoomFactor = 1.0;
-    m_offset = QPoint(0, 0);
-    update();
-}
-
-void ImageViewWidget::paintEvent(QPaintEvent *)
-{
-    if (m_pixmap.isNull())
-        return;
-
-    QPainter painter(this);
-    QPixmap drawn;
-
-    switch (m_zoomMode) {
-    case FitToScreen:
-        drawn = m_pixmap.scaled(size(), Qt::KeepAspectRatio, Qt::SmoothTransformation);
-        break;
-    case OriginalSize:
-        drawn = m_pixmap;
-        break;
-    case CustomZoom: {
-        QSize target(static_cast<int>(m_pixmap.width() * m_zoomFactor),
-                     static_cast<int>(m_pixmap.height() * m_zoomFactor));
-        drawn = m_pixmap.scaled(target, Qt::KeepAspectRatio, Qt::SmoothTransformation);
-        break;
-    }
-    }
-
-    clampOffset(drawn.width(), drawn.height());
-
-    int x = (width()  - drawn.width())  / 2 + m_offset.x();
-    int y = (height() - drawn.height()) / 2 + m_offset.y();
-    painter.drawPixmap(x, y, drawn);
-}
-
-void ImageViewWidget::keyPressEvent(QKeyEvent *event)
-{
-    if (event->key() == Qt::Key_Escape)
-    {
-        emit closeRequested();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_PageDown)
-    {
-        emit nextRequested();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_PageUp)
-    {
-        emit previousRequested();
-        event->accept();
-        return;
-    }
-
-    // Arrow keys for panning
-    constexpr int panStep = 50;
-    if (event->key() == Qt::Key_Left)
-    {
-        m_offset.rx() += panStep;
-        update();
-        event->accept();
-        return;
-    }
-    if (event->key() == Qt::Key_Right)
-    {
-        m_offset.rx() -= panStep;
-        update();
-        event->accept();
-        return;
-    }
-    if (event->key() == Qt::Key_Up)
-    {
-        m_offset.ry() += panStep;
-        update();
-        event->accept();
-        return;
-    }
-    if (event->key() == Qt::Key_Down)
-    {
-        m_offset.ry() -= panStep;
-        update();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_Slash)
-    {
-        zoomOriginal();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_Asterisk)
-    {
-        zoomFitToScreen();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_Plus)
-    {
-        zoomIn();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_Minus)
-    {
-        zoomOut();
-        event->accept();
-        return;
-    }
-
-    QWidget::keyPressEvent(event);
-}
-
-void ImageViewWidget::zoomIn()
-{
-    if (m_zoomMode == FitToScreen) {
-        // Calculate the current effective scale so zooming feels continuous
-        double sx = static_cast<double>(width()) / m_pixmap.width();
-        double sy = static_cast<double>(height()) / m_pixmap.height();
-        m_zoomFactor = std::min(sx, sy);
-    }
-    m_zoomFactor *= 1.25;
-    m_zoomMode = CustomZoom;
-    update();
-}
-
-void ImageViewWidget::zoomOut()
-{
-    if (m_zoomMode == FitToScreen) {
-        double sx = static_cast<double>(width()) / m_pixmap.width();
-        double sy = static_cast<double>(height()) / m_pixmap.height();
-        m_zoomFactor = std::min(sx, sy);
-    }
-    m_zoomFactor /= 1.25;
-    if (m_zoomFactor < 0.01)
-        m_zoomFactor = 0.01;
-    m_zoomMode = CustomZoom;
-    update();
-}
-
-void ImageViewWidget::zoomOriginal()
-{
-    m_zoomMode = OriginalSize;
-    m_zoomFactor = 1.0;
-    update();
-}
-
-void ImageViewWidget::zoomFitToScreen()
-{
-    m_zoomMode = FitToScreen;
-    m_offset = QPoint(0, 0);
-    update();
-}
-
-void ImageViewWidget::mousePressEvent(QMouseEvent *event)
-{
-    if (event->button() == Qt::LeftButton) {
-        m_dragging = true;
-        m_dragStart = event->pos();
-        m_offsetAtDragStart = m_offset;
-        setCursor(Qt::ClosedHandCursor);
-        event->accept();
-    }
-}
-
-void ImageViewWidget::mouseMoveEvent(QMouseEvent *event)
-{
-    if (m_dragging) {
-        m_offset = m_offsetAtDragStart + (event->pos() - m_dragStart);
-        update();
-        event->accept();
-    }
-}
-
-void ImageViewWidget::mouseReleaseEvent(QMouseEvent *event)
-{
-    if (event->button() == Qt::LeftButton && m_dragging) {
-        m_dragging = false;
-        setCursor(Qt::ArrowCursor);
-        event->accept();
-    }
-}
-
-void ImageViewWidget::clampOffset(int imgW, int imgH)
-{
-    // Only allow panning when the drawn image exceeds the widget
-    int overflowX = imgW - width();
-    int overflowY = imgH - height();
-
-    if (overflowX <= 0)
-        m_offset.rx() = 0;
-    else {
-        int limit = overflowX / 2;
-        m_offset.rx() = std::clamp(m_offset.x(), -limit, limit);
-    }
-
-    if (overflowY <= 0)
-        m_offset.ry() = 0;
-    else {
-        int limit = overflowY / 2;
-        m_offset.ry() = std::clamp(m_offset.y(), -limit, limit);
-    }
-}
diff --git a/imageviewwidget.h b/imageviewwidget.h
deleted file mode 100644
index bc0da7b..0000000
--- a/imageviewwidget.h
+++ /dev/null
@@ -1,48 +0,0 @@
-#pragma once
-
-#include <QWidget>
-#include <QImage>
-#include <QPixmap>
-#include <QString>
-#include <QPoint>
-
-class ImageViewWidget : public QWidget
-{
-    Q_OBJECT
-
-public:
-    enum ZoomMode { FitToScreen, OriginalSize, CustomZoom };
-
-    explicit ImageViewWidget(QWidget *parent = nullptr);
-
-    void setImage(const QString &path);
-    void zoomIn();
-    void zoomOut();
-    void zoomOriginal();
-    void zoomFitToScreen();
-
-signals:
-    void closeRequested();
-    void nextRequested();
-    void previousRequested();
-
-protected:
-    void paintEvent(QPaintEvent *event) override;
-    void keyPressEvent(QKeyEvent *event) override;
-    void mousePressEvent(QMouseEvent *event) override;
-    void mouseMoveEvent(QMouseEvent *event) override;
-    void mouseReleaseEvent(QMouseEvent *event) override;
-
-private:
-    void clampOffset(int imgW, int imgH);
-
-    QPixmap m_pixmap;
-    ZoomMode m_zoomMode = FitToScreen;
-    double m_zoomFactor = 1.0;
-
-    // Panning state
-    QPoint m_offset;        // current pan offset (pixels)
-    bool   m_dragging = false;
-    QPoint m_dragStart;
-    QPoint m_offsetAtDragStart;
-};
diff --git a/main.cpp b/main.cpp
deleted file mode 100644
index 6ce4d29..0000000
--- a/main.cpp
+++ /dev/null
@@ -1,13 +0,0 @@
-#include <QApplication>
-#include "mainwindow.h"
-
-int main(int argc, char *argv[])
-{
-    QApplication app(argc, argv);
-
-    MainWindow w;
-    w.resize(1200, 700);
-    w.show();
-
-    return app.exec();
-}
diff --git a/mainwindow.cpp b/mainwindow.cpp
deleted file mode 100644
index aa686c6..0000000
--- a/mainwindow.cpp
+++ /dev/null
@@ -1,280 +0,0 @@
-#include "mainwindow.h"
-#include "imagemodel.h"
-#include "imageviewwidget.h"
-
-#include <QFileSystemModel>
-#include <QTreeView>
-#include <QListView>
-#include <QLabel>
-#include <QSplitter>
-#include <QStackedWidget>
-#include <QDir>
-#include <QComboBox>
-#include <QVBoxLayout>
-#include <QStandardPaths>
-#include <QImageReader>
-#include <QHeaderView>
-#include <QScrollBar>
-#include <QTimer>
-#include <QEvent>
-#include <QKeyEvent>
-#include <QItemSelectionModel>
-#include <iostream>
-
-MainWindow::MainWindow(QWidget *parent)
-    : QMainWindow(parent)
-{
-    setupUi();
-    setupConnections();
-}
-
-void MainWindow::setupUi()
-{
-    // Folder model (left pane)
-    m_dirModel = new QFileSystemModel(this);
-    m_dirModel->setFilter(QDir::AllDirs | QDir::NoDotAndDotDot);
-    m_dirModel->setRootPath(QDir::homePath());
-
-    // Root chooser combo box
-    m_rootCombo = new QComboBox;
-    m_rootCombo->addItem("Home",     QDir::homePath());
-    m_rootCombo->addItem("Pictures", QStandardPaths::writableLocation(QStandardPaths::PicturesLocation));
-    m_rootCombo->addItem("File System", QDir::rootPath());
-
-    m_treeView = new QTreeView;
-    m_treeView->setModel(m_dirModel);
-    m_treeView->setRootIndex(m_dirModel->index(QDir::homePath()));
-    m_treeView->header()->hide();
-    m_treeView->setColumnHidden(1, true);
-    m_treeView->setColumnHidden(2, true);
-    m_treeView->setColumnHidden(3, true);
-
-    // Left pane: combo + tree inside a container widget
-    QWidget *leftPane = new QWidget;
-    QVBoxLayout *leftLayout = new QVBoxLayout(leftPane);
-    leftLayout->setContentsMargins(0, 0, 0, 0);
-    leftLayout->addWidget(m_rootCombo);
-    leftLayout->addWidget(m_treeView);
-
-    // Thumbnail model (center pane)
-    m_imageModel = new ImageModel(this);
-
-    m_listView = new QListView;
-    m_listView->setModel(m_imageModel);
-    m_listView->setViewMode(QListView::IconMode);
-    m_listView->setIconSize(QSize(128, 128));
-    m_listView->setGridSize(QSize(148, 168));
-    m_listView->setResizeMode(QListView::Adjust);
-    m_listView->setSelectionMode(QAbstractItemView::SingleSelection);
-    m_listView->setSpacing(4);
-    m_listView->setWordWrap(true);
-    m_listView->setTextElideMode(Qt::ElideRight);
-
-    // Preview pane (right)
-    m_previewLabel = new QLabel;
-    m_previewLabel->setAlignment(Qt::AlignCenter);
-    m_previewLabel->setMinimumWidth(300);
-
-    // Layout
-    QSplitter *rightSplitter = new QSplitter(Qt::Horizontal);
-    rightSplitter->addWidget(m_listView);
-    rightSplitter->addWidget(m_previewLabel);
-    rightSplitter->setStretchFactor(0, 3);
-    rightSplitter->setStretchFactor(1, 2);
-
-    QSplitter *mainSplitter = new QSplitter(Qt::Horizontal);
-    mainSplitter->addWidget(leftPane);
-    mainSplitter->addWidget(rightSplitter);
-    mainSplitter->setStretchFactor(1, 1);
-
-    m_browserPage = mainSplitter;
-
-    // Single image view
-    m_imageView = new ImageViewWidget;
-
-    // Stack to switch between browser and single image
-    m_stack = new QStackedWidget;
-    m_stack->addWidget(m_browserPage);
-    m_stack->addWidget(m_imageView);
-
-    setCentralWidget(m_stack);
-}
-
-void MainWindow::setupConnections()
-{
-    connect(m_rootCombo, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
-            [this](int index) {
-                QString rootPath = m_rootCombo->itemData(index).toString();
-                m_dirModel->setRootPath(rootPath);
-                m_treeView->setRootIndex(m_dirModel->index(rootPath));
-            });
-
-    connect(m_treeView, &QTreeView::clicked, this,
-            [this](const QModelIndex &index)
-            {
-                QString path = m_dirModel->filePath(index);
-                m_imageModel->setDirectory(path);
-                // Defer thumbnail load so the view has time to lay out items
-                QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
-            });
-
-    connect(m_listView, &QListView::clicked, this,
-            [this](const QModelIndex &index) { showPreview(index); });
-
-    connect(m_listView->selectionModel(), &QItemSelectionModel::currentChanged,
-            this, [this](const QModelIndex &current) { showPreview(current); });
-
-    connect(m_listView, &QListView::doubleClicked, this,
-            [this](const QModelIndex &index) {
-                if (m_imageModel->isFolder(index)) {
-                    QString path = m_imageModel->filePath(index);
-                    m_imageModel->setDirectory(path);
-                    // Update tree view selection to match
-                    QModelIndex dirIdx = m_dirModel->index(path);
-                    if (dirIdx.isValid())
-                        m_treeView->setCurrentIndex(dirIdx);
-                    QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
-                } else {
-                    enterSingleImageMode(index);
-                }
-            });
-
-    connect(m_imageView, &ImageViewWidget::closeRequested,
-            this, &MainWindow::leaveSingleImageMode);
-
-    connect(m_imageView, &ImageViewWidget::nextRequested, this, [this]() {
-        QModelIndex cur = m_listView->currentIndex();
-        int next = cur.isValid() ? cur.row() + 1 : 0;
-        while (next < m_imageModel->rowCount() && m_imageModel->isFolder(m_imageModel->index(next)))
-            ++next;
-        if (next < m_imageModel->rowCount())
-        {
-            QModelIndex idx = m_imageModel->index(next);
-            m_listView->setCurrentIndex(idx);
-            enterSingleImageMode(idx);
-        }
-    });
-
-    connect(m_imageView, &ImageViewWidget::previousRequested, this, [this]() {
-        QModelIndex cur = m_listView->currentIndex();
-        int prev = cur.isValid() ? cur.row() - 1 : 0;
-        while (prev >= 0 && m_imageModel->isFolder(m_imageModel->index(prev)))
-            --prev;
-        if (prev >= 0)
-        {
-            QModelIndex idx = m_imageModel->index(prev);
-            m_listView->setCurrentIndex(idx);
-            enterSingleImageMode(idx);
-        }
-    });
-
-    connect(m_listView->verticalScrollBar(), &QScrollBar::valueChanged,
-            this, [this]()
-            { loadVisibleThumbnails(); });
-
-    // Also catch resize — visible range changes when the viewport is resized
-    m_listView->viewport()->installEventFilter(this);
-}
-
-bool MainWindow::eventFilter(QObject *obj, QEvent *event)
-{
-    if (obj == m_listView->viewport() && event->type() == QEvent::Resize)
-        QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
-
-    return QMainWindow::eventFilter(obj, event);
-}
-
-void MainWindow::loadVisibleThumbnails()
-{
-    QModelIndex topLeft = m_listView->indexAt(QPoint(0, 0));
-    QModelIndex bottomRight = m_listView->indexAt(
-        QPoint(m_listView->viewport()->width() - 1,
-               m_listView->viewport()->height() - 1));
-
-    int first = topLeft.isValid() ? topLeft.row() : 0;
-    int last = bottomRight.isValid() ? bottomRight.row()
-                                     : m_imageModel->rowCount() - 1;
-
-    if (last < 0)
-        return;
-
-    std::cout << "loadVisibleThumbnails: " << first << " - " << last << "\n";
-    m_imageModel->requestThumbnails(first, last);
-}
-
-void MainWindow::showPreview(const QModelIndex &index)
-{
-    if (!index.isValid())
-        return;
-
-    QString path = m_imageModel->filePath(index);
-
-    QImageReader reader(path);
-    reader.setAutoTransform(true);
-    QImage image = reader.read();
-
-    m_previewLabel->setPixmap(
-        QPixmap::fromImage(image).scaled(
-            m_previewLabel->size(),
-            Qt::KeepAspectRatio,
-            Qt::SmoothTransformation));
-}
-
-void MainWindow::enterSingleImageMode(const QModelIndex &index)
-{
-    if (!index.isValid())
-        return;
-
-    QString path = m_imageModel->filePath(index);
-    m_imageView->setImage(path);
-    m_stack->setCurrentWidget(m_imageView);
-    m_imageView->setFocus();
-}
-
-void MainWindow::leaveSingleImageMode()
-{
-    if (isFullScreen())
-    {
-        if (m_wasFullScreen)
-            showFullScreen();
-        else
-            showNormal();
-    }
-    m_stack->setCurrentWidget(m_browserPage);
-    m_listView->setFocus();
-}
-
-void MainWindow::keyPressEvent(QKeyEvent *event)
-{
-    if (event->key() == Qt::Key_F11 && m_stack->currentWidget() == m_imageView)
-    {
-        if (isFullScreen())
-            showNormal();
-        else
-            showFullScreen();
-        event->accept();
-        return;
-    }
-
-    if (event->key() == Qt::Key_Return && m_stack->currentWidget() == m_browserPage)
-    {
-        QModelIndex current = m_listView->currentIndex();
-        if (current.isValid())
-        {
-            if (m_imageModel->isFolder(current)) {
-                QString path = m_imageModel->filePath(current);
-                m_imageModel->setDirectory(path);
-                QModelIndex dirIdx = m_dirModel->index(path);
-                if (dirIdx.isValid())
-                    m_treeView->setCurrentIndex(dirIdx);
-                QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
-            } else {
-                enterSingleImageMode(current);
-            }
-            event->accept();
-            return;
-        }
-    }
-
-    QMainWindow::keyPressEvent(event);
-}
diff --git a/mainwindow.h b/mainwindow.h
deleted file mode 100644
index 47a79d0..0000000
--- a/mainwindow.h
+++ /dev/null
@@ -1,44 +0,0 @@
-#pragma once
-
-#include <QMainWindow>
-
-class QTreeView;
-class QListView;
-class QLabel;
-class QStackedWidget;
-class QFileSystemModel;
-class QComboBox;
-class ImageModel;
-class ImageViewWidget;
-
-class MainWindow : public QMainWindow
-{
-    Q_OBJECT
-
-public:
-    explicit MainWindow(QWidget *parent = nullptr);
-
-private:
-    void setupUi();
-    void setupConnections();
-    void loadVisibleThumbnails();
-    void showPreview(const QModelIndex &index);
-    void enterSingleImageMode(const QModelIndex &index);
-    void leaveSingleImageMode();
-
-    void keyPressEvent(QKeyEvent *event) override;
-    bool eventFilter(QObject *obj, QEvent *event) override;
-
-    QFileSystemModel *m_dirModel;
-    ImageModel *m_imageModel;
-
-    QTreeView *m_treeView;
-    QComboBox *m_rootCombo;
-    QListView *m_listView;
-    QLabel *m_previewLabel;
-
-    QStackedWidget *m_stack;
-    QWidget *m_browserPage;
-    ImageViewWidget *m_imageView;
-    bool m_wasFullScreen = false;
-};
diff --git a/src/imagemodel.cpp b/src/imagemodel.cpp
new file mode 100644
index 0000000..3288ae0
--- /dev/null
+++ b/src/imagemodel.cpp
@@ -0,0 +1,171 @@
+#include "imagemodel.h"
+#include "thumbnailworker.h"
+
+#include <QDir>
+#include <QImageReader>
+#include <QFileInfo>
+#include <QFileIconProvider>
+
+ImageModel::ImageModel(QObject *parent)
+    : QAbstractListModel(parent)
+{
+    m_threadPool.setMaxThreadCount(QThread::idealThreadCount());
+
+    m_placeholder = QPixmap(128, 128);
+    m_placeholder.fill(Qt::lightGray);
+
+    QFileIconProvider iconProvider;
+    m_folderIcon = iconProvider.icon(QFileIconProvider::Folder);
+}
+
+ImageModel::~ImageModel()
+{
+    m_cancelFlag = true;
+    m_threadPool.waitForDone();
+}
+
+void ImageModel::setDirectory(const QString &path)
+{
+    m_cancelFlag = true;
+    m_threadPool.waitForDone();
+    m_cancelFlag = false;
+
+    beginResetModel();
+    m_items.clear();
+    m_pendingRows.clear();
+    m_currentDir = path;
+
+    QDir dir(path);
+
+    // Add subdirectories first
+    dir.setFilter(QDir::AllDirs | QDir::NoDot);
+    dir.setSorting(QDir::Name);
+    const auto dirs = dir.entryInfoList();
+    QPixmap folderPixmap = m_folderIcon.pixmap(128, 128);
+    for (const QFileInfo &d : dirs)
+    {
+        QString name = d.fileName();  // preserves ".." for the parent entry
+        m_items.append({d.absoluteFilePath(), name, folderPixmap, true, true});
+    }
+
+    // Then add image files
+    QStringList filters;
+
+    const auto formats = QImageReader::supportedImageFormats();
+    for (const QByteArray &fmt : formats)
+        filters << "*." + fmt;
+
+    dir.setNameFilters(filters);
+    dir.setFilter(QDir::Files);
+    dir.setSorting(QDir::Name);
+
+    const auto files = dir.entryInfoList();
+
+    for (const QFileInfo &file : files)
+    {
+        m_items.append({file.absoluteFilePath(), file.fileName(), m_placeholder, false, false});
+    }
+
+    endResetModel();
+}
+
+void ImageModel::requestThumbnails(int firstRow, int lastRow)
+{
+    if (m_items.isEmpty())
+        return;
+
+    firstRow = std::max(0, firstRow);
+    lastRow = std::min(lastRow, static_cast<int>(m_items.size()) - 1);
+
+    for (int row = firstRow; row <= lastRow; ++row)
+    {
+        if (!m_items[row].loaded && !m_items[row].isFolder)
+            queueRow(row);
+    }
+
+    // Optional: preload nearby rows
+    int buffer = 20;
+    for (int row = firstRow - buffer; row < firstRow; ++row)
+        if (row >= 0 && !m_items[row].loaded && !m_items[row].isFolder)
+            queueRow(row);
+
+    for (int row = lastRow + 1; row <= lastRow + buffer; ++row)
+        if (row < m_items.size() && !m_items[row].loaded && !m_items[row].isFolder)
+            queueRow(row);
+}
+
+void ImageModel::queueRow(int row)
+{
+    if (m_pendingRows.contains(row))
+        return;
+
+    m_pendingRows.insert(row);
+
+    auto *worker = new ThumbnailWorker(
+        m_items[row].path,
+        row,
+        &m_cancelFlag);
+
+    connect(worker, &ThumbnailWorker::finished,
+            this, &ImageModel::thumbnailReady,
+            Qt::QueuedConnection);
+
+    m_threadPool.start(worker);
+}
+
+QString ImageModel::filePath(const QModelIndex &index) const
+{
+    if (!index.isValid())
+        return {};
+
+    return m_items[index.row()].path;
+}
+
+bool ImageModel::isFolder(const QModelIndex &index) const
+{
+    if (!index.isValid() || index.row() >= m_items.size())
+        return false;
+    return m_items[index.row()].isFolder;
+}
+
+QString ImageModel::currentDirectory() const
+{
+    return m_currentDir;
+}
+
+int ImageModel::rowCount(const QModelIndex &) const
+{
+    return m_items.size();
+}
+
+QVariant ImageModel::data(const QModelIndex &index, int role) const
+{
+    if (!index.isValid())
+        return {};
+
+    const Item &item = m_items[index.row()];
+
+    if (role == Qt::DecorationRole)
+        return item.thumbnail;
+
+    if (role == Qt::DisplayRole)
+        return item.displayName;
+
+    return {};
+}
+
+void ImageModel::thumbnailReady(int row, const QImage &image)
+{
+    if (m_cancelFlag)
+        return;
+
+    if (row < 0 || row >= m_items.size())
+        return;
+
+    m_items[row].thumbnail = QPixmap::fromImage(image);
+    m_items[row].loaded = true;
+    m_pendingRows.remove(row);
+
+    QModelIndex idx = index(row);
+    emit dataChanged(idx, idx, {Qt::DecorationRole});
+}
diff --git a/src/imagemodel.h b/src/imagemodel.h
new file mode 100644
index 0000000..7586159
--- /dev/null
+++ b/src/imagemodel.h
@@ -0,0 +1,53 @@
+#pragma once
+
+#include <QAbstractListModel>
+#include <QPixmap>
+#include <QVector>
+#include <QThreadPool>
+#include <QSet>
+#include <atomic>
+#include <QIcon>
+
+class ThumbnailWorker;
+
+class ImageModel : public QAbstractListModel
+{
+    Q_OBJECT
+
+public:
+    explicit ImageModel(QObject *parent = nullptr);
+    ~ImageModel();
+
+    void setDirectory(const QString &path);
+    QString filePath(const QModelIndex &index) const;
+    bool isFolder(const QModelIndex &index) const;
+    QString currentDirectory() const;
+
+    void requestThumbnails(int firstRow, int lastRow);
+
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    QVariant data(const QModelIndex &index, int role) const override;
+
+    void thumbnailReady(int row, const QImage &image);
+
+private:
+    struct Item
+    {
+        QString path;
+        QString displayName;
+        QPixmap thumbnail;
+        bool loaded = false;
+        bool isFolder = false;
+    };
+
+    void queueRow(int row);
+
+    QVector<Item> m_items;
+    QThreadPool m_threadPool;
+    QPixmap m_placeholder;
+
+    QSet<int> m_pendingRows;
+    std::atomic_bool m_cancelFlag{false};
+    QIcon m_folderIcon;
+    QString m_currentDir;
+};
diff --git a/src/imageviewwidget.cpp b/src/imageviewwidget.cpp
new file mode 100644
index 0000000..f09ed6a
--- /dev/null
+++ b/src/imageviewwidget.cpp
@@ -0,0 +1,237 @@
+#include "imageviewwidget.h"
+
+#include <QPainter>
+#include <QKeyEvent>
+#include <QMouseEvent>
+#include <QImageReader>
+#include <algorithm>
+
+ImageViewWidget::ImageViewWidget(QWidget *parent)
+    : QWidget(parent)
+{
+    setFocusPolicy(Qt::StrongFocus);
+    setStyleSheet("background-color: black;");
+}
+
+void ImageViewWidget::setImage(const QString &path)
+{
+    QImageReader reader(path);
+    reader.setAutoTransform(true);
+    QImage image = reader.read();
+
+    if (!image.isNull())
+        m_pixmap = QPixmap::fromImage(image);
+    else
+        m_pixmap = QPixmap();
+
+    m_zoomMode = FitToScreen;
+    m_zoomFactor = 1.0;
+    m_offset = QPoint(0, 0);
+    update();
+}
+
+void ImageViewWidget::paintEvent(QPaintEvent *)
+{
+    if (m_pixmap.isNull())
+        return;
+
+    QPainter painter(this);
+    QPixmap drawn;
+
+    switch (m_zoomMode) {
+    case FitToScreen:
+        drawn = m_pixmap.scaled(size(), Qt::KeepAspectRatio, Qt::SmoothTransformation);
+        break;
+    case OriginalSize:
+        drawn = m_pixmap;
+        break;
+    case CustomZoom: {
+        QSize target(static_cast<int>(m_pixmap.width() * m_zoomFactor),
+                     static_cast<int>(m_pixmap.height() * m_zoomFactor));
+        drawn = m_pixmap.scaled(target, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+        break;
+    }
+    }
+
+    clampOffset(drawn.width(), drawn.height());
+
+    int x = (width()  - drawn.width())  / 2 + m_offset.x();
+    int y = (height() - drawn.height()) / 2 + m_offset.y();
+    painter.drawPixmap(x, y, drawn);
+}
+
+void ImageViewWidget::keyPressEvent(QKeyEvent *event)
+{
+    if (event->key() == Qt::Key_Escape)
+    {
+        emit closeRequested();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_PageDown)
+    {
+        emit nextRequested();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_PageUp)
+    {
+        emit previousRequested();
+        event->accept();
+        return;
+    }
+
+    // Arrow keys for panning
+    constexpr int panStep = 50;
+    if (event->key() == Qt::Key_Left)
+    {
+        m_offset.rx() += panStep;
+        update();
+        event->accept();
+        return;
+    }
+    if (event->key() == Qt::Key_Right)
+    {
+        m_offset.rx() -= panStep;
+        update();
+        event->accept();
+        return;
+    }
+    if (event->key() == Qt::Key_Up)
+    {
+        m_offset.ry() += panStep;
+        update();
+        event->accept();
+        return;
+    }
+    if (event->key() == Qt::Key_Down)
+    {
+        m_offset.ry() -= panStep;
+        update();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_Slash)
+    {
+        zoomOriginal();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_Asterisk)
+    {
+        zoomFitToScreen();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_Plus)
+    {
+        zoomIn();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_Minus)
+    {
+        zoomOut();
+        event->accept();
+        return;
+    }
+
+    QWidget::keyPressEvent(event);
+}
+
+void ImageViewWidget::zoomIn()
+{
+    if (m_zoomMode == FitToScreen) {
+        // Calculate the current effective scale so zooming feels continuous
+        double sx = static_cast<double>(width()) / m_pixmap.width();
+        double sy = static_cast<double>(height()) / m_pixmap.height();
+        m_zoomFactor = std::min(sx, sy);
+    }
+    m_zoomFactor *= 1.25;
+    m_zoomMode = CustomZoom;
+    update();
+}
+
+void ImageViewWidget::zoomOut()
+{
+    if (m_zoomMode == FitToScreen) {
+        double sx = static_cast<double>(width()) / m_pixmap.width();
+        double sy = static_cast<double>(height()) / m_pixmap.height();
+        m_zoomFactor = std::min(sx, sy);
+    }
+    m_zoomFactor /= 1.25;
+    if (m_zoomFactor < 0.01)
+        m_zoomFactor = 0.01;
+    m_zoomMode = CustomZoom;
+    update();
+}
+
+void ImageViewWidget::zoomOriginal()
+{
+    m_zoomMode = OriginalSize;
+    m_zoomFactor = 1.0;
+    update();
+}
+
+void ImageViewWidget::zoomFitToScreen()
+{
+    m_zoomMode = FitToScreen;
+    m_offset = QPoint(0, 0);
+    update();
+}
+
+void ImageViewWidget::mousePressEvent(QMouseEvent *event)
+{
+    if (event->button() == Qt::LeftButton) {
+        m_dragging = true;
+        m_dragStart = event->pos();
+        m_offsetAtDragStart = m_offset;
+        setCursor(Qt::ClosedHandCursor);
+        event->accept();
+    }
+}
+
+void ImageViewWidget::mouseMoveEvent(QMouseEvent *event)
+{
+    if (m_dragging) {
+        m_offset = m_offsetAtDragStart + (event->pos() - m_dragStart);
+        update();
+        event->accept();
+    }
+}
+
+void ImageViewWidget::mouseReleaseEvent(QMouseEvent *event)
+{
+    if (event->button() == Qt::LeftButton && m_dragging) {
+        m_dragging = false;
+        setCursor(Qt::ArrowCursor);
+        event->accept();
+    }
+}
+
+void ImageViewWidget::clampOffset(int imgW, int imgH)
+{
+    // Only allow panning when the drawn image exceeds the widget
+    int overflowX = imgW - width();
+    int overflowY = imgH - height();
+
+    if (overflowX <= 0)
+        m_offset.rx() = 0;
+    else {
+        int limit = overflowX / 2;
+        m_offset.rx() = std::clamp(m_offset.x(), -limit, limit);
+    }
+
+    if (overflowY <= 0)
+        m_offset.ry() = 0;
+    else {
+        int limit = overflowY / 2;
+        m_offset.ry() = std::clamp(m_offset.y(), -limit, limit);
+    }
+}
diff --git a/src/imageviewwidget.h b/src/imageviewwidget.h
new file mode 100644
index 0000000..bc0da7b
--- /dev/null
+++ b/src/imageviewwidget.h
@@ -0,0 +1,48 @@
+#pragma once
+
+#include <QWidget>
+#include <QImage>
+#include <QPixmap>
+#include <QString>
+#include <QPoint>
+
+class ImageViewWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    enum ZoomMode { FitToScreen, OriginalSize, CustomZoom };
+
+    explicit ImageViewWidget(QWidget *parent = nullptr);
+
+    void setImage(const QString &path);
+    void zoomIn();
+    void zoomOut();
+    void zoomOriginal();
+    void zoomFitToScreen();
+
+signals:
+    void closeRequested();
+    void nextRequested();
+    void previousRequested();
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+    void keyPressEvent(QKeyEvent *event) override;
+    void mousePressEvent(QMouseEvent *event) override;
+    void mouseMoveEvent(QMouseEvent *event) override;
+    void mouseReleaseEvent(QMouseEvent *event) override;
+
+private:
+    void clampOffset(int imgW, int imgH);
+
+    QPixmap m_pixmap;
+    ZoomMode m_zoomMode = FitToScreen;
+    double m_zoomFactor = 1.0;
+
+    // Panning state
+    QPoint m_offset;        // current pan offset (pixels)
+    bool   m_dragging = false;
+    QPoint m_dragStart;
+    QPoint m_offsetAtDragStart;
+};
diff --git a/src/main.cpp b/src/main.cpp
new file mode 100644
index 0000000..6ce4d29
--- /dev/null
+++ b/src/main.cpp
@@ -0,0 +1,13 @@
+#include <QApplication>
+#include "mainwindow.h"
+
+int main(int argc, char *argv[])
+{
+    QApplication app(argc, argv);
+
+    MainWindow w;
+    w.resize(1200, 700);
+    w.show();
+
+    return app.exec();
+}
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
new file mode 100644
index 0000000..aa686c6
--- /dev/null
+++ b/src/mainwindow.cpp
@@ -0,0 +1,280 @@
+#include "mainwindow.h"
+#include "imagemodel.h"
+#include "imageviewwidget.h"
+
+#include <QFileSystemModel>
+#include <QTreeView>
+#include <QListView>
+#include <QLabel>
+#include <QSplitter>
+#include <QStackedWidget>
+#include <QDir>
+#include <QComboBox>
+#include <QVBoxLayout>
+#include <QStandardPaths>
+#include <QImageReader>
+#include <QHeaderView>
+#include <QScrollBar>
+#include <QTimer>
+#include <QEvent>
+#include <QKeyEvent>
+#include <QItemSelectionModel>
+#include <iostream>
+
+MainWindow::MainWindow(QWidget *parent)
+    : QMainWindow(parent)
+{
+    setupUi();
+    setupConnections();
+}
+
+void MainWindow::setupUi()
+{
+    // Folder model (left pane)
+    m_dirModel = new QFileSystemModel(this);
+    m_dirModel->setFilter(QDir::AllDirs | QDir::NoDotAndDotDot);
+    m_dirModel->setRootPath(QDir::homePath());
+
+    // Root chooser combo box
+    m_rootCombo = new QComboBox;
+    m_rootCombo->addItem("Home",     QDir::homePath());
+    m_rootCombo->addItem("Pictures", QStandardPaths::writableLocation(QStandardPaths::PicturesLocation));
+    m_rootCombo->addItem("File System", QDir::rootPath());
+
+    m_treeView = new QTreeView;
+    m_treeView->setModel(m_dirModel);
+    m_treeView->setRootIndex(m_dirModel->index(QDir::homePath()));
+    m_treeView->header()->hide();
+    m_treeView->setColumnHidden(1, true);
+    m_treeView->setColumnHidden(2, true);
+    m_treeView->setColumnHidden(3, true);
+
+    // Left pane: combo + tree inside a container widget
+    QWidget *leftPane = new QWidget;
+    QVBoxLayout *leftLayout = new QVBoxLayout(leftPane);
+    leftLayout->setContentsMargins(0, 0, 0, 0);
+    leftLayout->addWidget(m_rootCombo);
+    leftLayout->addWidget(m_treeView);
+
+    // Thumbnail model (center pane)
+    m_imageModel = new ImageModel(this);
+
+    m_listView = new QListView;
+    m_listView->setModel(m_imageModel);
+    m_listView->setViewMode(QListView::IconMode);
+    m_listView->setIconSize(QSize(128, 128));
+    m_listView->setGridSize(QSize(148, 168));
+    m_listView->setResizeMode(QListView::Adjust);
+    m_listView->setSelectionMode(QAbstractItemView::SingleSelection);
+    m_listView->setSpacing(4);
+    m_listView->setWordWrap(true);
+    m_listView->setTextElideMode(Qt::ElideRight);
+
+    // Preview pane (right)
+    m_previewLabel = new QLabel;
+    m_previewLabel->setAlignment(Qt::AlignCenter);
+    m_previewLabel->setMinimumWidth(300);
+
+    // Layout
+    QSplitter *rightSplitter = new QSplitter(Qt::Horizontal);
+    rightSplitter->addWidget(m_listView);
+    rightSplitter->addWidget(m_previewLabel);
+    rightSplitter->setStretchFactor(0, 3);
+    rightSplitter->setStretchFactor(1, 2);
+
+    QSplitter *mainSplitter = new QSplitter(Qt::Horizontal);
+    mainSplitter->addWidget(leftPane);
+    mainSplitter->addWidget(rightSplitter);
+    mainSplitter->setStretchFactor(1, 1);
+
+    m_browserPage = mainSplitter;
+
+    // Single image view
+    m_imageView = new ImageViewWidget;
+
+    // Stack to switch between browser and single image
+    m_stack = new QStackedWidget;
+    m_stack->addWidget(m_browserPage);
+    m_stack->addWidget(m_imageView);
+
+    setCentralWidget(m_stack);
+}
+
+void MainWindow::setupConnections()
+{
+    connect(m_rootCombo, QOverload<int>::of(&QComboBox::currentIndexChanged), this,
+            [this](int index) {
+                QString rootPath = m_rootCombo->itemData(index).toString();
+                m_dirModel->setRootPath(rootPath);
+                m_treeView->setRootIndex(m_dirModel->index(rootPath));
+            });
+
+    connect(m_treeView, &QTreeView::clicked, this,
+            [this](const QModelIndex &index)
+            {
+                QString path = m_dirModel->filePath(index);
+                m_imageModel->setDirectory(path);
+                // Defer thumbnail load so the view has time to lay out items
+                QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
+            });
+
+    connect(m_listView, &QListView::clicked, this,
+            [this](const QModelIndex &index) { showPreview(index); });
+
+    connect(m_listView->selectionModel(), &QItemSelectionModel::currentChanged,
+            this, [this](const QModelIndex &current) { showPreview(current); });
+
+    connect(m_listView, &QListView::doubleClicked, this,
+            [this](const QModelIndex &index) {
+                if (m_imageModel->isFolder(index)) {
+                    QString path = m_imageModel->filePath(index);
+                    m_imageModel->setDirectory(path);
+                    // Update tree view selection to match
+                    QModelIndex dirIdx = m_dirModel->index(path);
+                    if (dirIdx.isValid())
+                        m_treeView->setCurrentIndex(dirIdx);
+                    QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
+                } else {
+                    enterSingleImageMode(index);
+                }
+            });
+
+    connect(m_imageView, &ImageViewWidget::closeRequested,
+            this, &MainWindow::leaveSingleImageMode);
+
+    connect(m_imageView, &ImageViewWidget::nextRequested, this, [this]() {
+        QModelIndex cur = m_listView->currentIndex();
+        int next = cur.isValid() ? cur.row() + 1 : 0;
+        while (next < m_imageModel->rowCount() && m_imageModel->isFolder(m_imageModel->index(next)))
+            ++next;
+        if (next < m_imageModel->rowCount())
+        {
+            QModelIndex idx = m_imageModel->index(next);
+            m_listView->setCurrentIndex(idx);
+            enterSingleImageMode(idx);
+        }
+    });
+
+    connect(m_imageView, &ImageViewWidget::previousRequested, this, [this]() {
+        QModelIndex cur = m_listView->currentIndex();
+        int prev = cur.isValid() ? cur.row() - 1 : 0;
+        while (prev >= 0 && m_imageModel->isFolder(m_imageModel->index(prev)))
+            --prev;
+        if (prev >= 0)
+        {
+            QModelIndex idx = m_imageModel->index(prev);
+            m_listView->setCurrentIndex(idx);
+            enterSingleImageMode(idx);
+        }
+    });
+
+    connect(m_listView->verticalScrollBar(), &QScrollBar::valueChanged,
+            this, [this]()
+            { loadVisibleThumbnails(); });
+
+    // Also catch resize — visible range changes when the viewport is resized
+    m_listView->viewport()->installEventFilter(this);
+}
+
+bool MainWindow::eventFilter(QObject *obj, QEvent *event)
+{
+    if (obj == m_listView->viewport() && event->type() == QEvent::Resize)
+        QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
+
+    return QMainWindow::eventFilter(obj, event);
+}
+
+void MainWindow::loadVisibleThumbnails()
+{
+    QModelIndex topLeft = m_listView->indexAt(QPoint(0, 0));
+    QModelIndex bottomRight = m_listView->indexAt(
+        QPoint(m_listView->viewport()->width() - 1,
+               m_listView->viewport()->height() - 1));
+
+    int first = topLeft.isValid() ? topLeft.row() : 0;
+    int last = bottomRight.isValid() ? bottomRight.row()
+                                     : m_imageModel->rowCount() - 1;
+
+    if (last < 0)
+        return;
+
+    std::cout << "loadVisibleThumbnails: " << first << " - " << last << "\n";
+    m_imageModel->requestThumbnails(first, last);
+}
+
+void MainWindow::showPreview(const QModelIndex &index)
+{
+    if (!index.isValid())
+        return;
+
+    QString path = m_imageModel->filePath(index);
+
+    QImageReader reader(path);
+    reader.setAutoTransform(true);
+    QImage image = reader.read();
+
+    m_previewLabel->setPixmap(
+        QPixmap::fromImage(image).scaled(
+            m_previewLabel->size(),
+            Qt::KeepAspectRatio,
+            Qt::SmoothTransformation));
+}
+
+void MainWindow::enterSingleImageMode(const QModelIndex &index)
+{
+    if (!index.isValid())
+        return;
+
+    QString path = m_imageModel->filePath(index);
+    m_imageView->setImage(path);
+    m_stack->setCurrentWidget(m_imageView);
+    m_imageView->setFocus();
+}
+
+void MainWindow::leaveSingleImageMode()
+{
+    if (isFullScreen())
+    {
+        if (m_wasFullScreen)
+            showFullScreen();
+        else
+            showNormal();
+    }
+    m_stack->setCurrentWidget(m_browserPage);
+    m_listView->setFocus();
+}
+
+void MainWindow::keyPressEvent(QKeyEvent *event)
+{
+    if (event->key() == Qt::Key_F11 && m_stack->currentWidget() == m_imageView)
+    {
+        if (isFullScreen())
+            showNormal();
+        else
+            showFullScreen();
+        event->accept();
+        return;
+    }
+
+    if (event->key() == Qt::Key_Return && m_stack->currentWidget() == m_browserPage)
+    {
+        QModelIndex current = m_listView->currentIndex();
+        if (current.isValid())
+        {
+            if (m_imageModel->isFolder(current)) {
+                QString path = m_imageModel->filePath(current);
+                m_imageModel->setDirectory(path);
+                QModelIndex dirIdx = m_dirModel->index(path);
+                if (dirIdx.isValid())
+                    m_treeView->setCurrentIndex(dirIdx);
+                QTimer::singleShot(0, this, &MainWindow::loadVisibleThumbnails);
+            } else {
+                enterSingleImageMode(current);
+            }
+            event->accept();
+            return;
+        }
+    }
+
+    QMainWindow::keyPressEvent(event);
+}
diff --git a/src/mainwindow.h b/src/mainwindow.h
new file mode 100644
index 0000000..47a79d0
--- /dev/null
+++ b/src/mainwindow.h
@@ -0,0 +1,44 @@
+#pragma once
+
+#include <QMainWindow>
+
+class QTreeView;
+class QListView;
+class QLabel;
+class QStackedWidget;
+class QFileSystemModel;
+class QComboBox;
+class ImageModel;
+class ImageViewWidget;
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    explicit MainWindow(QWidget *parent = nullptr);
+
+private:
+    void setupUi();
+    void setupConnections();
+    void loadVisibleThumbnails();
+    void showPreview(const QModelIndex &index);
+    void enterSingleImageMode(const QModelIndex &index);
+    void leaveSingleImageMode();
+
+    void keyPressEvent(QKeyEvent *event) override;
+    bool eventFilter(QObject *obj, QEvent *event) override;
+
+    QFileSystemModel *m_dirModel;
+    ImageModel *m_imageModel;
+
+    QTreeView *m_treeView;
+    QComboBox *m_rootCombo;
+    QListView *m_listView;
+    QLabel *m_previewLabel;
+
+    QStackedWidget *m_stack;
+    QWidget *m_browserPage;
+    ImageViewWidget *m_imageView;
+    bool m_wasFullScreen = false;
+};
diff --git a/src/thumbnailworker.cpp b/src/thumbnailworker.cpp
new file mode 100644
index 0000000..9b094ba
--- /dev/null
+++ b/src/thumbnailworker.cpp
@@ -0,0 +1,44 @@
+#include "thumbnailworker.h"
+#include <QImageReader>
+#include <QPainter>
+
+ThumbnailWorker::ThumbnailWorker(const QString &path,
+                                 int row,
+                                 std::atomic_bool *cancelFlag)
+    : m_path(path),
+      m_row(row),
+      m_cancelFlag(cancelFlag)
+{
+    setAutoDelete(true);
+}
+
+void ThumbnailWorker::run()
+{
+    if (*m_cancelFlag)
+        return;
+
+    QImageReader reader(m_path);
+    reader.setAutoTransform(true);
+
+    QImage image = reader.read();
+
+    if (*m_cancelFlag)
+        return;
+
+    if (!image.isNull())
+    {
+        // Scale to fit within 128x128 keeping aspect ratio
+        QImage scaled = image.scaled(128, 128,
+                                     Qt::KeepAspectRatio,
+                                     Qt::SmoothTransformation);
+        // Center on a 128x128 canvas with transparent/white fill
+        QImage thumb(128, 128, QImage::Format_ARGB32_Premultiplied);
+        thumb.fill(Qt::transparent);
+        int x = (128 - scaled.width())  / 2;
+        int y = (128 - scaled.height()) / 2;
+        QPainter painter(&thumb);
+        painter.drawImage(x, y, scaled);
+        painter.end();
+        emit finished(m_row, thumb);
+    }
+}
diff --git a/src/thumbnailworker.h b/src/thumbnailworker.h
new file mode 100644
index 0000000..5cdb7cd
--- /dev/null
+++ b/src/thumbnailworker.h
@@ -0,0 +1,26 @@
+#pragma once
+
+#include <QRunnable>
+#include <QObject>
+#include <QImage>
+#include <atomic>
+
+class ThumbnailWorker : public QObject, public QRunnable
+{
+    Q_OBJECT
+
+public:
+    ThumbnailWorker(const QString &path,
+                    int row,
+                    std::atomic_bool *cancelFlag);
+
+    void run() override;
+
+signals:
+    void finished(int row, const QImage &image);
+
+private:
+    QString m_path;
+    int m_row;
+    std::atomic_bool *m_cancelFlag;
+};
diff --git a/thumbnailworker.cpp b/thumbnailworker.cpp
deleted file mode 100644
index 9b094ba..0000000
--- a/thumbnailworker.cpp
+++ /dev/null
@@ -1,44 +0,0 @@
-#include "thumbnailworker.h"
-#include <QImageReader>
-#include <QPainter>
-
-ThumbnailWorker::ThumbnailWorker(const QString &path,
-                                 int row,
-                                 std::atomic_bool *cancelFlag)
-    : m_path(path),
-      m_row(row),
-      m_cancelFlag(cancelFlag)
-{
-    setAutoDelete(true);
-}
-
-void ThumbnailWorker::run()
-{
-    if (*m_cancelFlag)
-        return;
-
-    QImageReader reader(m_path);
-    reader.setAutoTransform(true);
-
-    QImage image = reader.read();
-
-    if (*m_cancelFlag)
-        return;
-
-    if (!image.isNull())
-    {
-        // Scale to fit within 128x128 keeping aspect ratio
-        QImage scaled = image.scaled(128, 128,
-                                     Qt::KeepAspectRatio,
-                                     Qt::SmoothTransformation);
-        // Center on a 128x128 canvas with transparent/white fill
-        QImage thumb(128, 128, QImage::Format_ARGB32_Premultiplied);
-        thumb.fill(Qt::transparent);
-        int x = (128 - scaled.width())  / 2;
-        int y = (128 - scaled.height()) / 2;
-        QPainter painter(&thumb);
-        painter.drawImage(x, y, scaled);
-        painter.end();
-        emit finished(m_row, thumb);
-    }
-}
diff --git a/thumbnailworker.h b/thumbnailworker.h
deleted file mode 100644
index 5cdb7cd..0000000
--- a/thumbnailworker.h
+++ /dev/null
@@ -1,26 +0,0 @@
-#pragma once
-
-#include <QRunnable>
-#include <QObject>
-#include <QImage>
-#include <atomic>
-
-class ThumbnailWorker : public QObject, public QRunnable
-{
-    Q_OBJECT
-
-public:
-    ThumbnailWorker(const QString &path,
-                    int row,
-                    std::atomic_bool *cancelFlag);
-
-    void run() override;
-
-signals:
-    void finished(int row, const QImage &image);
-
-private:
-    QString m_path;
-    int m_row;
-    std::atomic_bool *m_cancelFlag;
-};