Crayon Physics: A primer on physics-based puzzles

crayon_small_02.jpgIn the development of computer games, one of the most important underlying developments is the refinement of the so-called physics engine. Originally, each developer would independently define all reactions of the program to each input of the user. Obviously, this is very labour-intensive, so already from the start of computer-games different solutions were developed. The basic idea is to frame the game into the surrounding of a quasi-reality, so that the game itself can figure out how to react. In this approach, the central problem was to build a suitable quasi-reality. However, the big profit was that the quasi-reality became to some extent independent of the game itself, so it could be reused. Eventually, the development of such quasi-realities (or physics engines as they are usually called) became an industry of its own (see the historical survey by Calen Henry and Jacob Karsemeyer for an in-depth analysis).

Most games using such engines are shoot and race games, but there are also various puzzles that use the power of a quasi-reality.

The_Incredible_Machine_3.pngProbably the first puzzle game that used a (rather simplistic) physics engine was The Incredible Machine, originally developed by Kevin Ryan in 1992, but further developed for almost a decade (a screenshot taken from wikipedia is shown to the left). The underlying puzzle principle was the idea of a Rube Goldberg machine. A goal had to be reached (e.g. get a block into the bucket) by using various objects that all reacted (approximately) according to the rules of ordinary physics.  

There are many games in the app store that take this approach. They present an environment that acts like the real world, and ask you to reach a particular goal. Of course, the many simplistic maze puzzles (see my earlier post) also use a more-or-less refined physical reality. But the point here are the various puzzles in which the solution depends much more explicitly on your understanding of the effects of physics (as in the Incredible Machine). I will need a few posts to delve through the various kinds of puzzles that are developed on this basis. Summarizing, I have to say that I find all these physics-based puzzles one of the most innovative and interesting puzzles on the iPhone.

One of the most funny developments are the cartoonesque world’s, in which all objects look hand-drawn. This approach was first developed by Petri Purho in 2007, when he showed off his Crayon Physics game. At the time it was just a beta version, literally from the drawing board. It is now available for the iPhone as Crayon Physics Deluxe (a screenshot is shown at the top of this post). The idea is alike to the Incredible Machine, though the innovative aspect is that all objects that you want to use can be hand-drawn by using your finger.

The preliminary version of Purho’s puzzle-game immediately struck a chord with other developers, leading to various rip-offs using the same idea (links redirect to iTunes): iPhysics Lite, Touch Physics (and Touch Physics Lite), and Trace. All of these were even already available in the app store before the original finally made it in January 2009. I have only quickly looked at them, and though they are fun, they seem to be less polished than the original. The one aspect that makes Crayon Physics Deluxe really stand out from the rest is the possibility to use self-made hinges around a hand-drawn object revolves. This makes this game much deeper than the others.

134419-aquaforest.jpgAnother physics-based game that is in spirit much alike to Crayon Physics is Aqua Forest (shown to the right). Differently from the other physics-based puzzles, in Aqua Forest the object to be guided to a goal is a fluid! You literally have to poor the fluid from one place to another, using gravity (tilting the iPhone!) and using hand-drawn object to redirect the stream. I found the reactions of the game to my input a bit sluggish, but the concept is innovative and interesting enough to take a look.

Finally, I would like to mention one game that seems to use some physical properties, though I have no idea about the precise game-play because I didn’t have time to try it out: Glux. When you have any more insights on this game, please sound off in the comments!

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