Pretty neat!<p>My only real complaint was the browser (Firefox 32 beta) started off nice and smooth but by the 3rd or 4th level things were very choppy and uneven. It wasn't detecting my keystrokes very well during the choppy parts, causing me to waste missiles on the headcrab-ish guys.<p>Also, it wasn't entirely clear that I had to shoot the final boss guy when he was mad that I beat him at simon. I just sort of had to guess based on behaviors of other games I've played.
The Final boss fight was a little unintuitive for me. I thought it was completely a puzzle or a memory task, because you can't damage him right away. So I repeated his patterns with increasing difficulty, up to six beeps I think, waiting for him to implode from his anger. The fact that you need to shoot him while he's in the angry state wasn't obvious to me.