Very creative and fun game! It took me a while to understand how I could equip more slots. I didn't understand why a new row opened up for me, but I noticed that once you start filling up the slots, then you become OP very quickly. I used money mainly for HP and got to like the 5th or 6th floor. I'm not sure if there is an end but the enemies slowly multiplied so my run eventually ended.
My main recommendation would be for new slot items to be chosen separately from the "items" because once you get max item slots then you can't get more slot items. So you have to have at least 3 slots open if you want to keep filling up the slots.
Also, I ran into a bug when you click on play multiple times, it keeps spawning monsters so I had runs in the beginning when the rooms were literally filled with only monsters lol. Here is the screenshot. After that, I realized why my runs were so hard in the beginning and only clicked on play once.