Safe Harbor is an app I wrote years ago in C for Palm and PocketPC based on the plastic puzzle "Stormy Seas" by Binary Arts. It's small enough that experiments can be concluded quickly. One such experiment is porting to Java. This applet consists of only one file of AWT-aware Java. Nearly all of the code should work readily with other UI toolkits.

How to play? Move the pointy red boat into the harbor at the bottom. The blue wave bars slide side to side in order to line up openings for the boats to move into. The red boat can be turned if necessary by dragging its pointy end, but only if it's in a large enough open space. None of the other boats (which appear in Game 5) can turn, but they can move sideways.

Key handling. The "cross platform" code does this, but I haven't figure out how to get key events in AWT. Given key events you can play with a five-way alone.
State saving. Switch games and return and your undo stack remains. Reload the page, however, and all's lost. This is an AWT-specific thing. I'll worry about it when on a platform with better persistence.
Solving. The C code includes a brute-force puzzle solver. While it's nearly instantaneous on a desktop, it needed resources the 68K Palm never had and so I shipped with hard-coded solutions for every puzzle. When I ported Safe Harbor to Lua (for Foleo) there were some puzzles that couldn't be solved even on my desktop in an overnight run. So the solve feature tests both language and computer. Once I get it ported to Java we'll see how things look.