Game isn't challenging at all at this stage( It needs some level design.
Temporary game-speed increase seem like a bad idea to me. At least swap temporary and permanent controlls. Also to me it would be more comfortable if camera was controlled by mouse with wheel down instead of wasd.
When i press "quit" at the pause menu the game just freezes.
And last but not least: world surface looks like a macro shot of a snickers bar. For the love of god change it.

Idea is all right, but.
Gameplay is painfully slow. Or mb that's just web performance as mentioned.
Game controls are confusing as hell.
No difficulty curve, jast chaos everywhere.
Dunno what am i doing here 4 years late. Guess i gotta roast the site itself for it's recomenddations.