In my previous post I discussed puzzles in which objects have to be guided to a goal by using various forms of reflection. All those puzzles attempted (with more or less success) to present a realistic physical environment. In this post I will present another class of puzzles that also is based on reflection, but implemented in a more abstract manner. In these games reflection is only possible in right angles, and the puzzle consists of placing diagonally oriented mirrors in such a way that an object (balls, or a beam of light) will be guided to the goal (or goals).
The following puzzles in the app store implement this approach (links redirect to iTunes):
Lumen is made by high school student Bridger Maxwell, who got some news coverage in 2008 as he had built a custom-made multi-touch interface. Lumen already existed as a desktop game before he ported it to the iPhone.
The goal of the game is to direct a light-beam through all checkpoints in any order (see the screenshot at the top of this post for a typical set of checkpoints). To make it a bit more challenging, the checkpoints have a color, and the light beam has to match this color. To reach this goal, you are equipped with a laser beam that has to be positioned on the side of the board. You have to choose the color of the laser, and then reflect the beam around through the checkpoints using diagonal mirrors. To match the colors of the checkpoints, you can use filters that change the color of the laser beam. However, the number and kinds of changes of color are limited, so you’ll have to plan their usage wisely. As an example of the complexity that can arise, the solution to the puzzle at the top of this post is shown here to the left.
The game has an editor build in, and any puzzles you design can be submitted to the online repository. There is an active community producing puzzles, so currently there are over 2000 levels available. A selection of particularly good puzzles is stored inside the game, others can be easily downloaded from inside the application. The hard levels are challenging, though far from impossibly difficult. All in all, this is a polished offering with lots of puzzling pleasure.
Brain Puzzle is very similar to Lumen. There is also a beam of light that has to be guided through some waypoints by placing reflectors. Differently from Lumen, the start and end position of the beam is pre-set in this game and the number of reflectors that can be used is limited. Even stronger, all available reflectors have to be used, and all reflectors that are already fixed on the board at the start of the level also have to be used. The most interesting puzzles are the ones in which it is really easy to get directly to the goal, but then you are left with one reflector. Trying to find the roundabout route including the extra reflector is a nice challenge. It doesn’t get really difficult though, which is also impossible given the small board and the few variables that have to be considered.
Bumper Ball also uses diagonal reflection, but different from the previous two games it is used here to change the direction of moving balls. The balls in Bumber Ball move unstoppable in orthogonal direction, either left-right or up-down, bumping between walls or other obstacles. By activating a reflector (i.e. the little green corners in the screenshot shown to the right), the direction changes from left-right to up-down, or vice versa. By using these reflectors, the ball (or multiple balls in many levels) have to be guided to the goal (the yellow ‘U’ in the bottom right).
There are various obstacles and other problems to be passed, making the puzzles rather tricky at times. All reflectors are only used once, and after a ball has bumped into one, the reflector vanished again (though you can, and often have to, set one immediately there again). Also, there is no free choice of placing the reflectors (as in the previous games), but you are given the places where reflectors might be placed (as indicated by the green corners). The puzzles are mostly about finding the right order of (re)activating the reflectors. That sounds limited—and it indeed does not allow for really hard puzzles—but there is a large variety of other special effect that keep it interesting.
Visually, Bumper Ball is clearly less polished then the other offerings, but the levels are extremely well designed. Each level has a ‘trick’, a particular theme that you have to understand to be able to solve the puzzle. Once you got the trick, the level is mostly rather easily solved. However, getting the trick often evokes a really nice ‘aha’ effect, one of the hallmarks of great puzzle design. Often the name of the level also gives a hint. This approach makes for a really enjoyable puzzle-experience.
I only hope that the developers will refine the graphics, and also make it easier to place the reflectors. In many levels the timing of placing them is important, but it is rather difficult to correctly place them on the small screen of the iPhone. Still, this game was a pleasant surprise to me. From the looks, I did not expect it to be as enjoyable as it is. Don’t forget: a good puzzle is not about the polished graphics, it’s about the puzzle-structure and the level design!
[Update 7 March 2009] I have spend some more time looking for more background to these puzzles, because I expect the idea to have been around for much longer. I got a first hint through the flash game Reflections, which credits the game Aargon, originally published in 1999 by the company Twilight (sequels are still available from them). Although this puzzle likewise consists of a beam of light that has to be guided to a goal, the details seem different enough from the current iPhone games for them to be developed independently.