A very nice core mechanic! Allows every player to chose his own style. Love it when randomness is used in a clever way instead of simply being the player’s fate. Movement feels a bit weird at high speeds, as if you keep moving for a while (1/4 second or so) after letting the movement key go. Some of the levels can be completed simply by shooting all the enemies from far enough, maybe your weapon should have a limited range? There’s also a small problem with playing in web: you need to click on the game for it to gain focus at the start of each level, which is interpreted by the game as shooting, and you lose 1 ammo at the start of each level. No big deal since there’s plenty of ammo, but still a little bit annoying.
Anyways, very interesting submission, good job!