Hi,
Thanks for playing <3
You're definitely not the only person to experience slowness. I took a bunch of inefficient shortcuts later in the 7DRL and didn't think too much about them because I was testing and debugging in Chrome on a pretty beefy PC with plenty of RAM and CPU to burn. I didn't even really notice the slowdown issues until people complained about them after release and I tried it on another computer.
You'll be pleased to hear that I will soon be publishingjust published a version where I optimized a good bit of that slowdown away (and I fixed the firefox bug you mentioned too), so you may be able to play comfortably now-- please feel free to give it another try when you have a chance. And if it's still really bad, let me know so I can continue tinkering with it.
As for the rest of it, I'm waiting to actually add anything functional to the game until after the 7DRL judging is over. But I'm already working on that post-judging update-- "look" was a wishlist luxury-feature that I never got to, so I definitely will be adding it, no question. I also like your idea of modifier keys to make the arrows become diagonals, so I may steal that idea as well and add it as a movement option. STAY TUNED or don't. (Do.)