I really love the premise and the story and would totally want to see this being continued so hers a few issues I had;
- The upgrades are pretty long to get especialy in a jam context where you gotta play ton of games.
- There is no point in playing higher difficulty stage because they doesnt give more materials
- Killing the first boss over again still unlock new difficulty
- Enemies would sometimes not fade away and just continue on being immortals but still drop loot
Ideas
- Would be cool that each element had different attack area, for exemple: the wind attack will damage in a cross, the fire in a circle, ect..
- Being able to choose wich elements will be used and in which order
- Prerequisite for the next upgrade tier should count every previous upgrade instead of just the tier below
All in all the game is great and would definitly want to see more.