My idea is a retro fps (like Catacomb abyss), with a circle of death closing in.
The hardest thing for me in webGL is translucency, all the ordering, z-testing, depth-writing, blending and blend function madness. alpha testing is easy, but I want additive particles and transparent pickups.
It's the 17th hour, starting to loose focus. It's time for a nap, and call it a day :|
