I love what you've got so far, and given it's been updated within the last month I'm assuming it is still a very active development. I've played out to the extent of the alpha so far, love all 3 caves.
I didn't realize at first that the scattered pieces of wood were to access the second cave because you couldn't interact with them before you checked out the hole leading to the second cave sufficiently. So either being able to gather them early or adding the sparkle effect to them when they become relevant, or even both, could be a good addition.
I expect you have more planned for the townsfolk, perhaps as you sell them goods or complete tasks for them their sprite will increase in bust size as well, like the druid did as you gifted them potions. Will they get their own quest/story lines that can be pursued? Possibly with further boons and advantages you can take advantage of? I thought something was going to happen with the mana-tree girl for sure before I remembered that this is still in alpha stage XD.
Do you have plans for further colors? Or perhaps mixed colors, like say you aren't careful what mana you pick up and by having both a red and a blue mana they mix and you get 2 purple mana? Or is the chest just super good at keeping colors separated and the only way they mix is purposefully?
Regardless I'm excited to see more of this project. Oh, and almost forgot, I suppose you intend to add more exhaustion screens?