Press the left and right arrow keys to switch between what you want to draw. Press "space" for pen down and "u" for pen up. At any time, press "d" to hide the image and "space" to show it again, putting your pen down at the same time. The buttons in the lower left corner zoom in and out. Your drawing will not zoom in or out with the image behind it. I plan to make more of these, with different themes! :)
