Outstanding! Brotato eat your heart out.
Some really nice innovations here - the infinite world without wrapping feels really nice. The enemy spawns happening offscreen and them coming in is nice too.
Love the minimalist graphics. The idea that the enemies are also leveling up could make for some really interesting gameplay. Maybe the player could be given the choice of the enemy buffs too, might allow strategizing to try and make them weak against whatever line of buffs the player is taking for themselves.
I did find one degenerate strategy that worked too well in my win which was to just walk straight left and shoot right once I had more speed than them. Their chase pattern just lined them up and I didn't need to aim anymore. Could be countered with some more interesting enemy movement to force the player off their linear route.
Truly great little thing, I hope you develop it more, and make lots of more games in the future. I like your style.