PocketMatrix

Any game that uses the processor more will require more battery. Use low quality images and sounds (not COMPRESSED! Compression algorithms take up more processing power), and keep the main function loop as limited as possible. Just be very conservative about how much processing power your program uses. Like in Snails, when the enemy is thinking about their next move the blitting is slowed to 1 frame a second. That saves a little battery life, and speeds up the thinking process. Economy is what it's all about, be a penny pincher.