Thanks! I'm really glad you liked it :)
I'm sorry about your struggle with the icons e sprites. The pixel art is so small that some times assets blend together. I should have picked slightly different colors for the resource gathering nodes or used a highlight shader.
The upgrades bug was just some bad coding on my part:
if player.iron >= iron_cost:
player.iron -= iron_cost
if player.grass >= grass_cost:
player.grass -= grass_cost
if player.sticks >= sticks_cost:
player.sticks -= sticks_cost
if player.berries >= berries_cost:
player.berries -= berries_cost
upgrade()