Nice game!
I thought it was a really cool touch that the song started with the same sound you used for the gunshot!
I appreciate that switches were visibly connected to the gates they opened.
The minimal aesthetic was readable and functional. I liked the character's hat.
I'm not sure if it was mentioned that R restarts the level but making that clearer would be nice.
I think there are a lot of interesting ways to expand on the core ideas here, but overall you finished a good package of a game. Good work!