A very enjoyable experience. Very simple concept executed neatly: enemy behaviour is so simple yet the atmosphere keeps things tense enough. Couldn't get past the 4th room though. Part of it may be because I'm using a trackpad, so no mouse. Also was the "Your dead" on purpose there? sorry to be 'that guy' here but it ticked me off /j.
Oh and the best part of it for me was the music. Nice mixing there, and really feeds into the retro feel.
Btw Löve and Emscripten? Mad respect!