The World Ends With You.
Recently, I've been playing The World Ends With You, one of Square's non-Final Fantasy RPGs for the Nintendo DS. It's very engrossing; fast paced and highly configurable.
Game progress is broken up into very distinct stages, with clear goals for progressing to the next stage. Within each stage, game play is pretty much up to you. You can spend lots of time exploring, fighting, or even running around Shibuya shopping. Or you can focus directly on the tasks to progress to the next stage. I'm really enjoying the in-game flexibility to do whatever I want, whenever I want.
The game difficulty is also configurable at all times, in a variety of dimensions. And great rewards are available with the increased difficulty settings.
One very unique attribute of this game is the powering up system. Equipment (which grants abilities) earns experience; not just for fighting, but also when the game is shut down, and when it communicates wirelessly with other devices. The DS/TWEWY can detect WiFi communications from other TWEWY players (ESPers), DSs playing other games (Civvies), and non-DS devices (Aliens)! Very fun.
Tags: gaming nintendo