I'll have to echo g_o here and say that I was able to figure it out pretty quickly, but that's probably cause of having played Yu-Gi-Oh on a GBA emulator before. Even the Z/X controls just felt intuitive... But I understand that for people that don't have that experience, it's rather overwhelming.
A mass crossover debate with philosophers as a card game is a very interesting idea, but it seems like there were a lot of important corners that had to be cut during this week. It's a very polished entry, but in hindsight, it probably would've been better to develop the game more before doing so much polish. I understand that you unexpectedly got sick, so I can't really fault you too much here, but it is a shame that it turned out the way it did. Some important features like obtaining new cards, enemy AI using overlay/bench, and effect/spell/field/whatever cards didn't make it in, which means that the actual gameplay is reduced to "play philosopher combo that beats the enemy one and press End Turn a few times". The character sprites and dialog before matches are a cute addition.
It's hard to judge this as it is, because while it's functional, it's currently barely anything beyond that. I really hope you keep developing this, because it has a ton of potential. I wonder if you could get netplay working...