Great work, got a bit stuttery (sfx, frame rate) and glitchy around level 9.
The screen space used is a lot for a Web based game and reducing it but allowing full screen mode may help with performance.
Maybe a points allocation feature and other attributes could make for a more controllable weapon selection.
E.g. features unlock at 1,2,4,8,16 levels and each wave allows you to toggle 1,2,3 features.
And maybe other features e.g. shields, bombs, drones, special weapons, speed ect.