Scratch

What time is it? ... Actually, I was going to say Slime fighting time, but thats good enough.

Battle the slime king in an epic match to save your dimension from being swallowed by SPACE SLUGS! Race through time as you dodge slime balls, shoot pellets, and take down the slime king in this fast paced arcade style shooter.

It is intensely difficult, uberly hard, and frustratingly... frustrating. But seriously, this game is so hard, your head will explode. Although it is possible (I'm speaking from experience) it took even me at least 12 tries. Anyway, have a look.
http://scratch.mit.edu/projects/Eafu/987394
And PLEASE PLEASE PLEASE download it...or the music will sound awful, and the scripts won't work right.