Square Shooter

Controls: 

WASD for movement, mouse to aim

Hitting enemies charges a 2x fire rate boost meter. Press F to use this boost.

Power-ups drop occasionally, which grant temporary bonus attacks such as a triple shot.

Survive each wave and destroy all squares. Anything with a bright, square outline can hit you. Minimal style and difficult levels.

Edit: This game has memory issues, so it may lag at high graphic settings.