I super dig the aesthetic! I'm also intrigued by the weird, "unfair" feeling world. I was drawn in by the idea of everything being dependent on a coin flip. I was curious how that would be used.
For a game made in 48 hours, it's impressive. Seems like there's potential for weird mechanics: like if your "luck" generally improved as you played, that would make cards that trigger on a wrong guess grow weaker over time. Or if you have a "cursed" card with a huge benefit but that guarantees you'll lose the coin flip, that could synergize with passives that benefit you when you guess wrong, or dodge a boss attack that only hurts you if you guess right the turn before they use it.
Definitely could use UI polish (especially making damage dealt to opponents more obvious and maybe a way to view the contents of your deck), but it was a fun romp. (Also might need some kind of pity system: I missed something like 6 Heads call in a row on the final boss, despite having +10% heads luck and -5% tails luck.)
This was a cool 'venture. I dig the atmosphere you created. Thanks for making this!