Needs some extra love and attention 😉, but the beginning is there...
Gameplay
Very short and simple, but the idea of earning upgrades is present. More levels/challenges and upgrades and options would benefit the game a lot.
Graphics
Decent very simple graphics. Some extra effects or post processing would be cool. I think self made so kudos for that :)!
Audio
Main track is nice. Sound effects for jumping and getting to the flag would be a bonus in an update. Or some other SFX.
Theme
You do get upgrades, but some more would be beneficial for the game.
Devlog
You have one, but very short... Next time maybe try to explain a bit more what you did and why.
Good start but needs some extra content. Like to see new games from you on following jams