diff --git a/src/ViewportWidget.cpp b/src/ViewportWidget.cpp
index b2b2120..60dcdc7 100644
--- a/src/ViewportWidget.cpp
+++ b/src/ViewportWidget.cpp
@@ -702,8 +702,8 @@ void ViewportWidget::drawSelectionPlanes()
     };
 
     // XY Plane (Top)
-    QVector<GLfloat> xyQuad = { planeOffset, planeOffset, 0, planeOffset + planeSize, planeOffset, 0,
-                                planeOffset + planeSize, planeOffset + planeSize, 0, planeOffset, planeOffset + planeSize, 0 };
+    QVector<GLfloat> xyQuad = { planeOffset, -planeOffset, 0, planeOffset + planeSize, -planeOffset, 0,
+                                planeOffset + planeSize, -planeOffset - planeSize, 0, planeOffset, -planeOffset - planeSize, 0 };
     drawPlane(xyQuad, m_highlightedPlane == SketchPlane::XY);
 
     // XZ Plane (Front)
@@ -712,8 +712,8 @@ void ViewportWidget::drawSelectionPlanes()
     drawPlane(xzQuad, m_highlightedPlane == SketchPlane::XZ);
 
     // YZ Plane (Right)
-    QVector<GLfloat> yzQuad = { 0, planeOffset, planeOffset, 0, planeOffset + planeSize, planeOffset,
-                                0, planeOffset + planeSize, planeOffset + planeSize, 0, planeOffset, planeOffset + planeSize };
+    QVector<GLfloat> yzQuad = { 0, -planeOffset, planeOffset, 0, -planeOffset, planeOffset + planeSize,
+                                0, -planeOffset - planeSize, planeOffset + planeSize, 0, -planeOffset - planeSize, planeOffset };
     drawPlane(yzQuad, m_highlightedPlane == SketchPlane::YZ);
 
     glEnable(GL_CULL_FACE);
@@ -731,7 +731,7 @@ ViewportWidget::SketchPlane ViewportWidget::checkPlaneSelection(const QPoint& sc
     // Check front to back to handle overlaps
     // YZ plane (Right)
     intersection = unproject(screenPos, SketchPlane::YZ);
-    if (intersection.y() >= planeOffset && intersection.y() <= planeOffset + planeSize &&
+    if (intersection.y() >= -planeOffset - planeSize && intersection.y() <= -planeOffset &&
         intersection.z() >= planeOffset && intersection.z() <= planeOffset + planeSize) {
         return SketchPlane::YZ;
     }
@@ -746,7 +746,7 @@ ViewportWidget::SketchPlane ViewportWidget::checkPlaneSelection(const QPoint& sc
     // XY plane (Top)
     intersection = unproject(screenPos, SketchPlane::XY);
     if (intersection.x() >= planeOffset && intersection.x() <= planeOffset + planeSize &&
-        intersection.y() >= planeOffset && intersection.y() <= planeOffset + planeSize) {
+        intersection.y() >= -planeOffset - planeSize && intersection.y() <= -planeOffset) {
         return SketchPlane::XY;
     }