I would say this is a very interesting concept but if you want to take this a little further there are a few things I would change. 

For one, don't use the shift keys or the control keys because I find myself accidentally turning on the filter keys or pressing Ctrl + S.

I would also say limit the options for keys to as few buttons as possible, you don't have to use all the buttons on the keyboard.

I think that overall the game moves too fast for the controls, which would be very fun if the learning curve was a bit longer! Overall definitely interesting and worth a play! Good work.

A cool concept well executed, enjoyed it a lot.

The game would probably benefit from a more zoomed out view or a small heads up warning where enemies will appear so the player has more time to make up a plan and adjust to the controls.

Hello

Well then was some original idea, I like that. It was a challenge to focus on changing keys and shoot at the same time and I like that challenge!

Have to warn other players to play it on fullscreen since some keys cause browser to switch focus out of the game, so I had to use the mouse to focus again.

cool kinda td game haha consider making control buttons maybe pop up bigger somewhere. Hard to concentrate on the image of the keyboard and the enemies at the same time