Thanks so much for the helpful feedback :)
UX: Yeah, I will be adding Gamepad support at some point. Also touch for mobile :)
WebGL: It's great to hear you had no performance issues, even with all those tabs open ;)
Keyboard: Were you able to reassign keys correctly to your preference? In other words, if you click on the game options icon (next to the play icon) and then clicked on a one of the keyboard assignments (it should then start flashing) and then pressed a key on your QWERTZ keyboard, does the correct key show in the menu and does it then work instead of the default. (Reassigning keys works fine on my QWERTY keyboard but I'm not sure, for instance, if you press Z on your keyboard if it will show as Z or Y)