Scratch is 10! Based on the game 10 bullets. You have 10 neutrons to destroy as many atoms as possible. There is a cascade effect as atoms are destroyed. Press space to fire a neutron or click the mouse. If you play with the settings inside then you can make this pretty intense/easy. Let me know in the comments if you find some good settings.
Apart from backdrops this is 100% pen Thanks to @Numbers_Letters for introducing me to the 10 Bullets game. Music by She - Atomic. Speech synthesis from http://codewelt.com/proj/speak