What makes Prelude special, though, is the RPG element added that gives it an extra level of strategy and a 'level grind' high familiar to anyone who has played a MMOG. After every level, you want to spend your hard earned coin to upgrade your weapons and see how they effect the next round. I lost a whole morning to this game.
The simplicity and addictiveness of this title and Winterbells (see directly below) make me long somewhat for the days I was in the mobile space. Prelude, unfortunatly, wouldn't translate very well into mobile (at least not that I can see) but Winterbells would work perfectly. If someone isn't already trying to contact the developer to seek out mobile licensing rights -- they should be.
Update: I fixed the broken link to the game. Apologies. I hope someone out there took the time to google the game on their own and enjoyed it.