The total size, although smaller than 10KB, could definitely have been squeezed down much further. But since the limit was 10KB it was hard to find the motivation to do so.

The basic game mechanic is almost identical to "Noiz", a PalmOS game: http://www.asahi-net.or.jp/~cs8k-cyu/palm/noiz.html

Noiz has much more complex patterns of "enemies" to avoid, though. If you don't have a Palm device handy, the source is still pretty fun to pick through.