This is a miniature ascii text version of the classic Space Invaders game. Live demo on http://jsfiddle.net/6hb5yfbw/1/ (click on link to play). It is written in the smallest amount of JavaScript that I could squeeze it. Entire game is 527 bytes! The core logic of the game is a single function that fits in less than 140 bytes.

Space-Invaders-game.html

<h1><pre id=x><script>function a(a,b,f,j){for(j="",a=0;10>a;a++){for(b=0;16>b;b++)f=b==c&9==a?3:0,a==e&&(f=g&1<<b-d?1:f),a==e+1&&(f=w&1<<b-d?1:f),f=b==h&a==i?1==f?4:2:f,f=9>e-!w+1?f:5,j+=".#i^@*"[f];j+="\n"}x.innerHTML=j}function b(){var c=0,j=0,c=1<<h-d;g-=j=i==e?g&c:0,w-=c=i==e+1?w&c:0,i-=j|c?10:1,g|w?0:(d=4,e=0,g=w=Z),(g|w)&1<<15*(f>0)-d?(e++,f=-f):d+=f,a(),setTimeout(b,300)}var c=8,d=4,e=0,f=1,g=w=Z=85,h=0,i=-1;this.onkeydown=function(b){b=event.keyCode,c-=37==b&c>0,c+=39==b&15>c,38==b&0>i&&(h=c,i=8),a()},b()</script>