This is an absurdly impressive amount of content and UI work for a game jam game! A large variety of cards, pretty responsive crafting and card usage controls, and a nice upgrade system. Well done on the content creation front!
We lost our first run before learning how to use the energy cells; you have to upgrade from the bottom most row first. The second run, we got to an absurdly powerful state. Just like in other deck builders, say no to skills that don't fit your build. Our final set was just loaded with some Strength increasing abilities and cantrip-y feature type abilities. By the time the final fights came around, the character was unstoppably powerful; very similar to how deckbuilding dungeoncrawlers can end up. While the game can be rough around the edges, the fact that we got drawn in enough to play through twice tells you something!
The adherence to the theme is a bit rough; you have Only One day to survive is a good theme, but not reinforced much in game. There's a numeric clock up top ticking up, but perhaps some popups to say "you only have X time left" or somesuch. We think the screen darkened a bit and the encounters got a little more difficult as time went on, which is definitely in the right direction for reinforcing the theme. Overall, great game!