In my previous post I discussed various puzzles that used the principle of “movement-until-blocked” to transform a simple grid into a more or less complex maze. In a comment to that post, Bob Hearn drew my attention to another such puzzle in the app store that I had missed (iTunes link): Riddle Racer (a free version to try it out is also available). The goal of this puzzle is to move the car to the centre of the board with the help of the orange pylons. Both the car and the pylons can be moved, but only if they are blocked at some point by the car or another pylon.
Riddle Racer is a remake of a puzzle known under the names UFO, Galactic Transit, Lunar Lockout, and Pete’s Pike. John Rausch gives some background on the origin and development:
“Lunar Lockout was originally called UFO. UFO was created by Hiroshi Yamamoto and presented by Nob Yoshigahara [see my post on his puzzle Rush Hour, MC] in February 1998 at the Third Gathering for Gardner in Atlanta, Georgia. The handout had sample problems using a 9×9 board that turned out to be much larger than necessary for reasonably difficult problems. The board was subsequently reduced to 5×5. Papers with forty or more sample problems for the 5×5 board have been circulating in the puzzle collecting community since the presentation.”
The name UFO was changed to Lunar Lockout by Thinkfun (formerly Binary Arts) for the commercial version (shown here to the left) released in the spring of 2000. The name ‘Lunar Lockout’ is a trademark of Thinkfun. Recently, Thinkfun re-introduced the game under the name ‘Pete’s Pike’ (shown here to the right).
Even with the small board of 5×5, the game has a high complexity, as analyzed in this nice article by John Rausch. Although most puzzles do not need many moves to get to the finish, they are still quite difficult for humans to solve because the state-tree is often very wide. There are many alternatives routes in the state-tree maze, and many of these routes look confusingly similar. The puzzle shown in the top right picture only needs 9 moves, but it took me quite a while to find the right route.
Given the fact that Riddle Racer is based on a really terrific puzzle, with a good selection of levels, makes it a little gem in the app store. The graphic design is a bit simplistic, but it gets the job done. Pieces are moved with swipes, there is full undo, you can freely choose levels, and it even offers help when you get too frustrated. So, actually is done right for a nice puzzle app. In the end, the beauty lies in the puzzling fun, and not in the graphical experience. Unfortunately, the puzzle is rather badly rated in the app store. It doesn’t deserve that.