Played around a bit and didn't get it at first, so had to reread the instructions.
Since there is no UI at all, i didn't understand the attack instructions at all. Had to try everything out to get the hang of it. Once i tried everything there wasn't much else to see really.
Anyway, the graphics are fine. Everything looks sharp and is actually a pleasure to look at for what it is. Having fire and smoke be cubes make sense with that theme.
The attacks i don't understand. It seems it's just differently colored ways to destroy cubes? The explosions are the coolest of course. It seems the explosion sound gets increasingly quiet once i pressed F and upgraded their frequency. I guess the different attacks could be some mechanic to interact with different type of cubes? Explosions just being a straight 3x3x3 aoe, while another attack is transmitted to all neighbouring cubes of the same type? Something like that.
I saw that there are some coins dropping sometimes and i guess this is what will be used to upgrade and maybe buy the weapons in the first place?
The game starts off with a big cube, but maybe it should really start of with a single one or just a few and let the player upgrade the amount. This could be great to introduce more weapons. Regenerating the cubes seems pretty fast too, maybe that can also be tied to some upgrade?
Having the upgrade system and some UI will probably be the best next step as it will help to get an idea what this could become. Also cube types that do something.