Have you checked out Save The Planet yet?
Check out the Windows version here.
Check out the Android version here.
Fast dynamic gameplay against multiple enemy types.
Featuring 6 mutators, 8 enemy types, multiple waves, special weapons and old school graphics.
Windows controls:
Left - Rotate counterclockwise
Right - Rotate clockwise
Z - Shoot
X - Shield
A - Special (use when planet changes colour)
Android controls:
Hold top left - Rotate counterclockwise
Hold bottom left - Rotate clockwise
Tap top right - Shoot
Tap bottom right - Shield
Tap center - Special (use when planet changes colour)