Have You Played... Outland?
Red vs Blue
Outland doesn't have a unique bone in its red and blue body. You can reach new areas in the world after unlocking abilities, like Metroid; you navigate the environment with the agility of the Prince Of Persia; and you take out baddies by changing the colour of your character, like Ikaruga. Its that last one that makes Outland a great 2D action-platformer, rather than just a good one, though.
If you're up against a predominantly red enemy, then you must switch from your own red-hot summer bod for a cooler, winter-y blue, in order to deal damage. This ability really shines during Outland's massive boss battles. These big bads fire both red and blue attacks your way, forcing you to shift between the two pigmentations as quick as you can. It's manic, sure, but so satisfying when you pull it off.
It isn't all about being aggressive, though: playing with colouration is a must for getting around. You'll fall straight through blue platforms if you're wearing your red skin, and vice-versa. Some of the more complex platforming sequences that pop up can test your patience, but, again, you feel like some sort of glowing god when you reach the end of one of these tougher sections.
Who needs wholly original ideas when smushing together mechanics from other games provides something as wonderful as this?