Iv been itching for a Binding of Isaac clone, so I will be interested to see where you go with this. Looks like there is no end goal yet, so I just played around till I got bored. Had fun, but the lack of a long term goal does limit how long I could enjoy it. Random costs for shop ideas is interesting, though get upgrades for 0 cost almost feels like cheating. It seems a bit odd that you can go though doors while there are enemies in the room and the teleport recharging whenever I pass though a door means I can fully recharge it by jumping back and fourth through a single door.
Also found a glitch where if you enter the door way right on the side you can walk all the way up without being taken to next room.
Thanks for the fun demo, good luck with the game!