Couldn't quite beat it on my first try, but barely won when I tried a 2nd time! So difficulty was just right.
Theme is quite solid since the enemies, enemy types and turret upgrades are added over time. The doors were kind of forced as in they didn't make any difference to the gameplay or anything, could've been anything else as well. (The door sprites looked good tho!)
The sound effects were great, this kind of game would feel very empty without them. I read in another comment that it was your first time making music? If that's true you did AMAZING!
I'm a musician so let me break it down a little further:
+ There is no random dissonance or unintentional weird note choices which are typical when I hear someone's first electronic track.
+The sound choices are all solid and nothing feels too out of place.
+Important for a game, it doesn't get annoying hearing it on a loop while playing the game. Also it isn't obvious when the song loops (Like a weird pause or something where you can easily hear "oh here it loops")
+I love the lead synth doing the slides/bends, it really makes the track " lift off "
+The drums aren't just a kick/snare loop and you have some details there.
+The biggest plus is you have DYNAMICS and CONTRAST between the song sections, the drums go in and out. Melody stops playing as well. You have different combinations of the instruments playing so it feels fresh as the song goes on!
Now there's still stuff that could be improved, but these wouldn't be as relevant to game jams more like making music in general:
- The mixing, while not bad could be better. I think it works since you have so few instruments and good sound choice. (Each occupy their own frequency area quite nicely)
-Arrangement wise you don't have any instrument playing chords. Songs often have at some points some kind of comping instrument playing chords. Not having any can make it seem hollow. (Having chords can complicate mixing however since chords are often in a similar frequency range as the melody. )
-You could add more effects like delays or maybe a modulation effect like flanger/chorus for some part. This is common in electronic to have more contrast and movement. Also doing automation on these effects and pan/volume etc. is what really makes a track pop!
But yeah the music "negatives" are major nitpicking, I'm jealous you did so great on your first time.
Solid game entry, sorry for the novel about music in the middle in my review haha