I worked on this game for the jam, thanks for playing it and thanks for saying all the nice things. Unfortunately due to a mistake/unforseen act of god, the UI doesn't actually communicate anything about the game, which we realize now after watching other people play it. The "feed" screen UI for some reason has a white background to the inventory, which indicates that the food is selected (and thus, pressing the big "feed" button in the screen will do something).
It actually doesn't- the idea is that you select which items to feed the monster by clicking on them one-by-one (you might have only found loads of poison and not want to use all of it, for instance). The "Feed" button just ends the day and feeds whatever you have selected (in your case, nothing). We, the three who made it, all "knew" how to feed it, so this in hindsight glaring player feedback issue never game up as we were making it.
Other issues we probably should have noticed but didn't, and I'm not sure if you encountered:
- unclear what the goal even is if you didn't read the itch.io page
- "hunger", "trust", "strength". We don't actually tell you what any of these bars do, nor do we animate them moving. We hint at their functions with notes, but nobody figured out that the effect of food scales with how much the monster trusts you, for example. Or that you run faster at higher trust.
- Also unclear what effect food has, even moreso with trust scaling their effect. The descriptions give you a hint--hedgehogs reduce its strength similar to poison, for instance--but only one person who wasn't us ever figured out their effects enough to make a meaningful gameplay choice about feeding strategies. And that involved us having to tell him the effect of trust on the bars.
- Forest is kind of barren- it has 3 spawners close together, but many players explored every corner as it's quite large.
Hope this helps you wring some enjoyment out of it.