Needs pause when lose mouse focus. Other than that - not a bad approach to tetris

Cool game, just had some trouble with the controls. First few times I played, the keyboard controls were not working at all, so I tried mouse controls but they didn't work very well. Often the piece wouldn't move as far as I wanted or would even move the wrong direction. After a few refreshes, the keyboard controls were working, which is a much better experience, but one problem: the up and down keys also scrolled the browser window up/down a little bit, which was kind of annoying.

I hope this feedback is helpful because I love the game otherwise. Super fun concept and I could see myself playing this for a long time. I just want to play with keyboard controls without the window scrolling up/down.

Suggestion: maybe a "next block" indicator off to the side?

Edit: It seems that the first problem I was having, is that when you click the game to start, only mouse controls work - you have to press a key to start the game if you want to play with keyboard. Maybe this could be made clearer, or changed, because to me it just seemed like the game wasn't working right.

I can see where you were going with this, and you've got a pretty creative idea, but the mouse-only controls render this much harder to play than it should.

I strongly recommend you add keyboard controls (WASD or arrows, doesn't matter) whenever you get the chance.