This should be fixed in the Beta Build 0.13, Which is a download since browsers cant really run this game above 40FPS
I played the beta version and i LOVED it. It looked amazing (especially the glow from the minerals and the lava) and had an actual challenge. Collecting all of the secrets and achievements were fun, but more achievements would be better. All the problems I had were fixed and there were more levels to play.
Keep on the good work!