One of the one I wanted to play when I saw it on twitter. I thought the battles were going to be annoying with it being based on a coin toss, however that was not the case. First Having the enemies die in one hit was a simple and brilliant solution as it avoids going back and forth with one enemy. When was this decision made, early on of after playtesting? Finally the potions also helped fight against the randomness.
I think this concept can be carried further for a full game. Like buying different coins, loaded(higher chance of one side), coins with status bonus(landing on one side recharges 1 hp). and the theme of the world based around coins.
Well done.