Hey! It's a bit clunky at this prototype stage, but the main point as of now is to dig through that wall you found (by clicking left mouse button with a pickaxe in your hand) and find some locations with enemies and crystals hidden inside - then sell whatever resources you get. Aand in the esc menu you can find a Help Manual option to see all the relevant controls
You might be stuck if the character doesn't fit in the hole you dug up or if there's a loose voxel in your way - known issue :(
We're rebuilding the whole game in Unreal right now, where we'll add actual story-based gameplay and MUCH nicer UX/UI, while saving the mining concept. But thank you for trying out this version! .D