• the original game needed far more memory than is available in the Nintendo DS handheld system
• the original was designed to work on a system that also supports virtual memory, something that can't be easily done on the DS
• Q2 stresses the CPU far more than Q1 does, and a lot of time had to be spent getting the game itself (not including rendering) running at a decent rate
• the models and levels in Q2 are far more detailed than the ones in Q1, and this was originally too much for the DS' GPU to handle (oh, and there's a lot more texture detail, too!)
  

• The Game
• every single level within the game can be loaded and played in single-player mode
• there is currently no wifi multiplayer
• the game can be run with either the demo or full retail pak files
• there is full control configuration
• there is an on-screen keyboard for use in-game and with the console
• there are eight "touch-buttons" which allow you quick access to in-game functions
• both manual and automatic game saving works
• mods and total conversions do not work, and are unlikely ever to - however new levels can be used
• Graphics
• nearly-all of the graphical effects have been have been moved to the DS' 3D hardware
• most world textures are rendered correctly
• particles are supported, however sprites are not
• animated model skins are properly supported
• although the game does not use lightmapping, dynamic lighting is fully-functional
• Sound
• there's a full-blown custom ARM7 sound effects system, and it totally r0x0rs
• the sound system uses proper spatial positioning (it is stereo though...) - plug it into your speakers and subwoofer to hear all the effort I put into this!
• Supported cards:
  
• 'Proper' SuperCards, eg the Lite, SD, MiniSD, and CF. The SuperCard Rumble and SuperCard One are not compatible.
• 'Perfect' M3s, eg the Lite Perfect, the Mini SD Perfect, and the SD Perfect. The Mini SD Pro, SD Pro, and Lite Pro are not compatible.
• EZ-Flash cards which have a slot-2 component and can play GBA games over 32MBit, eg EZ 3-in-1, EZ 4, EZ 5
• G6 Flash

Via Drunken Coders