Very pleasing game to play ! It is very well polished and it is a blast (ahah) to shot and move around
The premise of the Heat system is interesting, but it felt to me as just the justification of the game beeing more difficult the more you advance (wich is normal), and I didn't felt it as a "cost"
I don't know if there's a solution for this game to have more agency, like if you don't shoot at ennemies during a certain time the heat reduces, and the act of doing that unlocks other things (I'm in suppositions-territory, I'll let you think of solutions for this if you want to go firther ^^)
Also it was cool that the items served different purpose, there was definitively choices to make before picking up them like waiting for some amount of Heat or having more enemies on screen
Again, it was very cool to play this game, good job !