Thanks for the feedback as always!
Soon after implementing the shop I wasn't really happy with it. I'm thinking of changing this in the future. I have a few ideas but I'm not sure just yet. I may very well go back to the upgrade-tree like system I had before. I imagine it'd be easier to implement in Godot than in GameMaker so that's certainly an option.
This would clean up the shop a bit too.
I'll probably have items be a one-time purchase and then the player can equip whatever they've purchased in-between stages.
As a side note a unit can only have one item at a time but this isn't communicated yet. The 5th skill slot is reserved in-case I need it in the future (like for boss specific mechanics for example)
Stages will get more interesting in the future for sure! I just wanted a base to work on and adding randomised terrain is a bit more work.
I might try and limit the scope of the game a bit and just have that previous arena mode you mentioned. We'll see. Alpha is alpha!
The house could be used as a place to heal in the future. We'll see what happens when I shake things up a bit! ^_^
I'll try something in the next update in regards to the tile items!
As always, thank you so much!