I've spent the last 10 months writing a new game which I've now released through the !Store on RISC OS.
Full source code is included for tinkering and making new games. Its in BBC BASIC V, which I found surprisingly powerful with its ability to call operating system SWI's directly.
Its a 2.5D/3D space game in the style of Gyruss/Tempest featuring ~45 minutes of original music (using MP3 Streaming).
The game runs at 60hz in 800x600. I also looked into making the game compatible with other RISC OS systems and managed to run it on pandaboard, beagleboard, Iyonix, ARM X6, Virtual Acorn as well as the Pi.
Having not used RISC OS before, I found the Raspberry Pi a nice cheap way to experiment with it. I released games in the 90's for the Amiga as shareware using AMOS and the experience was similar but a bit more low level. So I intend to share a BASIC library that makes it easier to write games.