Damn this is one smooth browser game, you put the green/white girl platformer to shame in terms of performance. If space is not used for anything else, let it be an alternative for jumping. Same goes for up arrow, Z is for console babbys. The pixel art looks great, but it's a shame you decided to vomit on it with those lighting effects. Collecting floating "coins" is some of the most uninspired design I've seen in a while too. Overall, it runs and looks great, but the game direction is unclear.
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I'll put space as a jump input, though it might feel awkward to attack. Don't worry about everything else, it's temporary. The lighting is a halfassed solution because the actual lighting system in Godot is super unoptimized, and the coins were just put in as an objective for demo players. You'll mostly be fighting enemies and bosses in the real game.