Thanks for the feedback
I'm getting pretty big generated JS from dart2js right now, that may be the resource hog you're mentioning.
Tonight was spent adding a smoke attack that engulfs an enemy in LOS blocking smoke. I also made a whitelsit of map seeds, that should prohibit some unfortunate generating times (I did once encounter an invalid start room, gonna have to improve the generator a bit more).
Other than that, I started attempting to balance the turn times of actions a bit to make it semi-playable.
Tomorrow I can hopefully squash a few more bugs, add a second level and some more sprites, and perhaps a victory condition (reaching the exit). Then polishing and finishing on saturday.