Super Crossfire

Super Crossfire is an Arcade Game-style Indie Game Shoot Em Up game for PC and iOS heavily inspired by Space Invaders, with the added twist that the player can press a button to flip from the bottom of the screen to the top. It's got some RPG Elements too.

It's available on the official website of its creator, Radiangames, and on Desura.

Super Crossfire contains examples of:

 * Critical Existence Failure: This is how death works.
 * Difficulty By Acceleration
 * Excuse Plot: You blow up aliens. There you go, that's the plot.
 * Game Level
 * Healing Checkpoint: Your armor is fully replenished at every checkpoint. Doubles as Level Up Fill Up, since every checkpoint gains you a level as well.
 * Mercy Invincibility
 * Pinball Scoring: Basically, there are an extra two zeroes at the end of your score.
 * Point Build System
 * RPG Elements: In the form of unlockable upgrades and a Point Build System for level-ups.