I really like this concept! The barrier to entry is super high, though. Not only do I have to read the descriptions of what each button does below, I also have to figure out what each monster does, and with the timer it's too difficult to understand quickly. I understand that time limits the amount of explanation you can do, but for a super low-effort explanation, I would have put text on the screen that says "Add a room type and a monster to each room before time runs out!" and then put little colored arrows next to each one. Red up arrow increases HP, red down arrow decreases it (and you can put multiple for more damage), blue arrow increases or decreases happiness, yellow arrow increases or decreases speed. Just my suggestion for future situations like this - remember that it doesn't have to be great, just readable :)