cool game, a bit short but a nice concept, I feel like having trinkets on the creatures would help spice the game up a bit.
like having it be so every other time instead of getting a creature you have a way to upgrade all the creatures, or maybe 1 creature. For example: give 1 attack to all creatures with no effect or give 2 health for all creatures that give 2 attack so you could build around getting those "trinkets" or powerups.