Marshmallow Duel DS is a standalone 2-player game built for the Nintendo DS console, although it can also be run under Windows via emulators. The entire game engine was created from scratch, using the amazing PALib DS development library.
MDuel DS offers deceptively simple gameplay mechanics in a style similar to Super Smash Bros and is fully configurable through a plethora of options. The game engine is designed to manage low-level sprite routines efficiently and easily, leaving the higher-level game logic abstracted into its own tier of classes. The source code is released publicly under the GPL and can also be downloaded from the game website.