i finished lvl.3, aka demo's end; played with pad.
Overall thoughts
i like the tron+geometry wars vibes
destructibility i like a lot, and probably it's your main focus. "see how every enemy and the arena itself is destructable" etc
gameplay is solid, but with only one enemy there is only so much i can say about combat feel.
i don't have anything bad to say about your demo. the main problem is that you need tons of enemies, guns, ship parts and bosses.
it's no joke when you have isaac as competitor.
Random stuff i noted
lmao what's a pre-prototype
the first screen where you look around it's cool but imo too long;
when you choose the memorycard for your saturn: the light border on the cards seems too little, it's probably just a problem caused by the camera angle
"go back" with B/circle button in menu ui imo it's a must;
making the enemy spawn after you open the gates is imo not a good choice (visually). maybe you spawn them "deactivated", then you open the door and then you ativate the ai
you need "something" to happen when you kill an enemy to visualize the kill(beyond energy/money drop). The destruction fucks with this, bacause some enemies are still alive when they are only "a few bits of poligons left" and i have to double check them.
lmao a slotmachine room. i lmao, but if this is the only "shop" i'll suggest you to make also a classic one, and leave the slots for risky "rare" drops. a way for better players to have more fun.
also since this is an isaac game, you probably need a powerup per level to incentivize exploration of the dungeon.
boss door should be different, beside on the map (again, isaac)
when exp flies to you, it shouldn't have an "OnExitTrigger" or similar effect imo. when the energy locks you it flies to you and should not lose you
when you change dungeon floor, it seems "level" is reset.
i like music blasting, but it seems to increase and decrease volume on it's own. you should make "maximum volume" in your audio mixer. also an option to change volume while pausing
i like a lot that razor boss on lvl.3 has more parts to be broken than previous versions.
about the boss, i like his intro a lot, but ofc in three levels i was already "get over with it". it's probably more a recycle content problem that will disappear once u have more bosses
i dunno if i like that if you dont "aim" your ship goes places when you shoot