• Draw the circle in perspective (i.e., an ellipse) inside the square in perspective (i.e., a quadrilateral), then check whether your drawing is correct.[br]• Click the 'Compare' button repeatedly to switch between your circle and the correct circle.[br]• Use the gray slider and the blue slider to adjust the field of view (FOV) of the square/circle, respectively.[br]• Keep the FOV low (~20-30°) for a more natural look.[br]• Use Ctrl+Z/Ctrl+Y to undo/redo strokes. You can also use the arrows in the top-right corner.