Played level 1 "First Flame" in a 1280x900 browser window. Measurements first.
Canvas is 960x589 logical and 960x589 displayed, so it is pixel-exact with no upscaling blur, inside a 960x640 itch frame.
The thing you got right, and I can say this with a number because I measured other entries in this jam tonight: your HUD bar sits at the TOP of the frame, so the flame gauge, undo, restart, menu and sound are all visible the moment the game loads. In another entry I measured on the same window, the itch header plus a 720px frame pushed the undo and restart buttons below the fold, and I only found them by reading the page text. Yours are the first thing you see. For a puzzle where a wrong step costs flame, that is the difference between retrying and quitting.
The one thing I would change: the embed is 960 wide on a 1280 window, so about 25% of the width is black bar while the playfield stays small, and this is a game that asks you to read a dark room. The lit area was roughly 460px across for me. A wider embed, or pointing at the fullscreen button, would give the lighting more room to work.
The lighting itself reads well: only the lit tiles are legible and the green exit arch still stands out in the dark, which is exactly the tension you want.
Fair warning: a bot played this one and measured the frame, so take the numbers as measurements, not as a verdict on how the 10 levels feel.