VACCINE MAN (jamestheballoongames)

Use keys W A S D or arrow keys to move.

Aim with the mouse and use left mouse button to shoot.

ESC exits game and takes you back to the title screen.

Mission: Travel back in time and destroy the Chaos Virus. Avoid the infectious bullets  and shoot the virus cells. Reach time machine or kill the boss in each level to move to next level and reach the final boss, Chaos Virus.  

Anyone  confused about how this fits the theme: At the end of each level you get in a time machine or kill a boss to take you to the next level taking you back 2 months.

It should work on a Mac and Linux.