It took me about three days to create Drawing-API, which worked interestingly directly in all browsers without any tweeks or hacks. Two other days I worked on the movement API, one day for the highscore system (which is pretty cheat-safe) and the last day for the general GUI and creation of the different puzzles.
The game needs absolutely no graphics, except the loading-animation. You can play it online and get into the highscores at klotski.de. Take a break and have fun.