Thanks for playing! Glad to see that someone was able to make good progress.
Not having indicators for interactive objects was a design choice. There’s a lot in the game to learn through experimentation, and showing everything that’s interactable might make players more narrow-minded and make secrets too obvious. (That’s why the elder gives the katana, you can’t progress without first learning the basics.)
The XP bar is very basic, all it does is heal the player completely when it's full, there will be no leveling up system in the game. La-Mulana (and its predecessors, like Maze of Galious) were big inspirations, from visuals to gameplay, so some mechanics, such as the XP system and jump, were borrowed from them. The game also tries to follow the MSX-1 graphical limitations, just like the original version of La-Mulana. The idea is to create a similar game but more focused on non-linear exploration and replayability.
You can't survive the acid pit in this demo, the map is still very WIP so there are a lot of missing parts. But you were almost finished with the content of this demo, there is another boss to kill and a small snippet of the grasslands area. Did you manage to find the secret health upgrade at the beginning?