diff --git a/gridpreview.cpp b/gridpreview.cpp
index ab8a3a3..8aee464 100644
--- a/gridpreview.cpp
+++ b/gridpreview.cpp
@@ -12,19 +12,67 @@ void GridPreview::setSize(int newWidth, int newHeight)
 {
     width = newWidth;
     height = newHeight;
+
+    update();
+    emit updatedContents();
 }
 
 void GridPreview::addLine(Line &line)
 {
     lines.push_back(line);
+
+    update();
+    emit updatedContents();
 }
 
 void GridPreview::removeLine(int index)
 {
     lines.removeAt(index);
+
+    update();
+    emit updatedContents();
 }
 
-QString GridPreview::toLuaTable()
+void GridPreview::setLineColor(int index, QString color)
+{
+    lines[index].setColor(color);
+
+    update();
+    emit updatedContents();
+}
+
+void GridPreview::setLineStartPoint(int index, int x, int y)
+{
+    lines[index].setStartPoint(x, y);
+
+    update();
+    emit updatedContents();
+}
+
+void GridPreview::setLineEndPoint(int index, int x, int y)
+{
+    lines[index].setEndPoint(x, y);
+
+    update();
+    emit updatedContents();
+}
+
+int GridPreview::getWidth()
+{
+    return width;
+}
+
+int GridPreview::getHeight()
+{
+    return height;
+}
+
+const Line &GridPreview::getLine(int index)
+{
+    return lines.at(index);
+}
+
+const QString GridPreview::toLuaTable()
 {
     QString output(tableTemplate.arg(width).arg(height));
     QString linesSubTable = "";
@@ -37,13 +85,15 @@ QString GridPreview::toLuaTable()
     return output.arg(linesSubTable);
 }
 
-void GridPreview::paintEvent(QPaintEvent *event)
+void GridPreview::paintEvent(QPaintEvent *)
 {
     QPainter painter(this);
     QPen pen(Qt::black, 2);
     painter.setPen(pen);
     QBrush brush(Qt::black);
-    bool widthBased = rect().width() > rect().height();
+    double aspectRatio = (double) rect().width() / rect().height();
+    double cellAspectRatio = (double) width / height;
+    bool widthBased = aspectRatio > cellAspectRatio;
     int cellSize = widthBased ?
                        rect().height() / height :
                        rect().width() / width;
@@ -101,9 +151,54 @@ void GridPreview::paintEvent(QPaintEvent *event)
     }
 }
 
-QColor GridPreview::colorFromString(QString color)
+const QColor GridPreview::colorFromString(const QString color)
 {
     if (!colorMap.contains(color))
         return colorMap[QString("red")];
     return colorMap[color];
 }
+
+void GridPreview::mouseMoveEvent(QMouseEvent *event)
+{
+    if (!mouseCaptured) {
+        return;
+    }
+}
+
+void GridPreview::mousePressEvent(QMouseEvent *event)
+{
+    mouseCaptured = true;
+
+    QPoint gridPos = localMousePosition(event);
+
+    std::cout << gridPos.x() << ',' << gridPos.y() << std::endl;
+}
+
+void GridPreview::mouseReleaseEvent(QMouseEvent *event)
+{
+    mouseCaptured = false;
+}
+
+const QPoint GridPreview::localMousePosition(QMouseEvent *event)
+{
+    QPoint position(event->position().toPoint());
+    return snapToGrid(position.x(), position.y());
+}
+
+const QPoint GridPreview::snapToGrid(int x, int y)
+{
+    double aspectRatio = (double) rect().width() / rect().height();
+    double cellAspectRatio = (double) width / height;
+    bool widthBased = aspectRatio > cellAspectRatio;
+    int cellSize = widthBased ?
+                       rect().height() / height :
+                       rect().width() / width;
+
+    int areaWidth = cellSize * width;
+    int areaHeight = cellSize * height;
+
+    int offsetX = (rect().width() - areaWidth) / 2;
+    int offsetY = (rect().height() - areaHeight) / 2;
+
+    return QPoint(1 + (x - offsetX) / cellSize, 1 + (y - offsetY) / cellSize);
+}
diff --git a/gridpreview.h b/gridpreview.h
index 3ae6e28..7b65b55 100644
--- a/gridpreview.h
+++ b/gridpreview.h
@@ -3,25 +3,46 @@
 
 #include <QWidget>
 #include <QPainter>
+#include <QMouseEvent>
+#include <iostream>
 #include "line.h"
 
 class GridPreview : public QWidget
 {
     Q_OBJECT
-public:
-    explicit GridPreview(QWidget *parent = nullptr);
-    void setSize(int newWidth, int newHeight);
-    void addLine(Line &line);
-    void removeLine(int index);
-    QString toLuaTable();
-    void paintEvent(QPaintEvent* event);
-    QColor colorFromString(QString color);
-private:
     int width = 5, height = 5;
     QVector<Line> lines {};
     QMap<QString, QColor> colorMap;
     const QString tableTemplate = "return {\n    width = %1,\n    height = %2,\n    lines = {\n%3\n    }\n}";
+
+    bool mouseCaptured = false;
+public:
+    explicit GridPreview(QWidget *parent = nullptr);
+    void setSize(int newWidth, int newHeight);
+
+    void addLine(Line &line);
+    void removeLine(int index);
+
+    void setLineColor(int index, QString color);
+    void setLineStartPoint(int index, int x, int y);
+    void setLineEndPoint(int index, int x, int y);
+
+    int getWidth();
+    int getHeight();
+    const Line& getLine(int index);
+
+    const QString toLuaTable();
+    void paintEvent(QPaintEvent* event);
+    const QColor colorFromString(const QString color);
+
+    void mouseMoveEvent(QMouseEvent* event);
+    void mousePressEvent(QMouseEvent* event);
+    void mouseReleaseEvent(QMouseEvent* event);
+
+    const QPoint localMousePosition(QMouseEvent* event);
+    const QPoint snapToGrid(int x, int y);
 signals:
+    void updatedContents();
 };
 
 #endif // GRIDPREVIEW_H
diff --git a/line.h b/line.h
index 23ee306..72d9d45 100644
--- a/line.h
+++ b/line.h
@@ -5,6 +5,9 @@
 
 class Line
 {
+private:
+    int startX, startY, endX, endY;
+    QString color;
 public:
     Line();
     void setStartPoint(int x, int y);
@@ -16,9 +19,6 @@ public:
     int getEndY();
     QString getColor();
     QString toLuaTable();
-private:
-    int startX, startY, endX, endY;
-    QString color;
 };
 
 #endif // LINE_H
diff --git a/mainwindow.cpp b/mainwindow.cpp
index 2740a6e..c85352f 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -6,9 +6,32 @@ MainWindow::MainWindow(QWidget *parent)
     , ui(new Ui::MainWindow)
 {
     ui->setupUi(this);
+    QObject::connect(ui->gridPreview, &GridPreview::updatedContents,
+                     this, &MainWindow::onGridUpdated);
+    ui->gridPreview->updatedContents();
 }
 
 MainWindow::~MainWindow()
 {
     delete ui;
 }
+
+void MainWindow::onGridUpdated()
+{
+    ui->textPreview->setPlainText(ui->gridPreview->toLuaTable());
+
+    ui->spinGridWidth->setValue(ui->gridPreview->getWidth());
+    ui->spinGridHeight->setValue(ui->gridPreview->getHeight());
+}
+
+void MainWindow::on_spinGridWidth_valueChanged(int arg1)
+{
+    ui->gridPreview->setSize(arg1, ui->gridPreview->getHeight());
+}
+
+
+void MainWindow::on_spinGridHeight_valueChanged(int arg1)
+{
+    ui->gridPreview->setSize(ui->gridPreview->getWidth(), arg1);
+}
+
diff --git a/mainwindow.h b/mainwindow.h
index f7a3da3..d79e7dd 100644
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -17,6 +17,14 @@ public:
     MainWindow(QWidget *parent = nullptr);
     ~MainWindow();
 
+public slots:
+    void onGridUpdated();
+
+private slots:
+    void on_spinGridWidth_valueChanged(int arg1);
+
+    void on_spinGridHeight_valueChanged(int arg1);
+
 private:
     Ui::MainWindow *ui;
 };