Good start, very arcade like. I like the bloom fx on the graphics.  It does run pretty fast chrome, a lot more playable from FF which doesn't have gpu acceleration. The speed seems dependent on frame rate. One option is to pick a target framerate (like 60) and calculate the ratio between that target and the actual frame rate. Then multiplying your movements (enemies, bullets, etc..) by that fraction should yield identical movement regardless of high or low frame rates. 
For instsance:
fps = 60.0 * 1.0/actualFramerate
bulletSpeed = 3 * fps