A downloadable game
Dyox is a homebrew PSP game built in 2006. Inspired by the classic game Oxyd, Dyox is a 2D puzzle game where you control a marble and interact with level objects to gain access to each level's goal.
A development diary written when the game was released is available: http://brightnightgames.com/games.php?game=dyox&sec=development
See the included ReadMe. The game should install and run on PSPs with any CFW version. Includes a build for CFW 1.50, though you will probably want to use the 1.00 version, which should work in all other CFW versions. The 1.00 version also runs well in the PPSSPP emulator.