This is a solid entry and really great use of the "only one" limitation. Your one-screen/ one-level is designed well and has a very clear flow from top left to bottom right. The placement of platforms that restrict backwards movement forces the player to try out different paths in order to collect the keys. Feedback: The game's difficulty curve is maybe a bit too gentle. As a result, it can feel a little repetitive. Consider introducing more keys sooner. Especially if they're in similar positions as previous levels.
and also, thank you for playing our game Impulse and leaving such a wonderful review :)