The game is really fun, with lot of good idea, and you included the theme insect and reuse/recycle in an intelligent way.
I like the tutorial screen, you can see the control, playing and shoot to launch the game is good idea, the cartoon graphics is really cool too. I like the animation of the train too, that put a context, and add interest.
The game need little of adjustement for a better bullet hell top down shooter arena. First the screen become speedly very confuse, with ennemies, bullets, and damage effect on the all screen.
The idea of the broken glaces to show the damage is good and immersive but finally is not good in this kind of game i think,because that hiding a lot of things.
The camera is maybe to near of the character or character is to big, there is a problem with that i think.
I’ve played and study some bullet hell shooter, and the ennemies have regular pattern so this “easy” to learn and anticipated shoot, but scrolling is forced so you can dodge and learn it to win. In an Arena bullet hell shooter like your game, ennemies follow you, and adjust position in function of your move, so dodging bullet is pure reflexe, the big mecha character you control (that seems logical but not pratical) have difficulty to avoid clouds of bullets, and ennemies shoot paquet of bullets its strange very confuse.
Fortunally the damage are not heavy, and you can easily change for a new mech, the idea of changing mech is excellent and the player character is small and can easily dodge attack (i like the sound of walking).
Maybe reduce the hitbox of the mech, the hitbox of the bullet hell shooter is generally very small just a circle on the center of the sprite.
Killing boss and clean area/level to acquire a new weapons give a progression sensation, unifortunally the levels are graphically the same (but its a jam game its ok), using train to change level is a good idea. Next level had nests farther to the train, its interesting in level design because the train fabricate energy and mecha remplacement so we need to take care when we go farther, well done.
About new weapons, i prefered the base weapon because it had heaviest firerate, and ennemy give lot of energy bonus.
I had a technical issue on web version (firefox browser), when i start a level and kill the first ennemy, i have a lag, the game charging maybe effects, i think its strange, if you not find why i suggest to load the effect before and keep it into memory, i don’t know the functionnement of “godot engine” but i think you miss one thing.
In resume : Very cool gamejam game, you need to try to made game less confuse, good work !