You can only mine blocks on the frontier: the edge of the discovered area. Mining a safe block cascades: connected blocks of the same type flood open in a wave. Some blocks hide monsters, and mining one releases it. Sometimes that is an accident, sometimes it is a hunt.
Prefer a classic minesweeper read? Turn on the numbers in Options: faint counts of the monsters hiding around each revealed tile.
On the surface, daytime lights the whole map: mine freely. At night (and always underground) darkness rules: you can only work on lit ground, and monsters spawn on revealed-but-dark tiles. Torches, your campfire, watchtowers, forges and altars each cast light; upgrading the campfire widens the camp's light and every torch's. Survive to dawn and the day brings a small reward. Light is not decoration, it is territory.
Tap a monster to strike it with your equipped weapon (bare fists if the weapon slot is empty). Your weapon's tier must be at least the monster's tier to hurt it at all. Hits knock monsters back a full tile and interrupt their attack; fast tapping can hold a single attacker off a torch, but monsters rarely come alone. Released monsters always path toward your nearest structure: torches are bait, walls of light are strategy. Ghosts are the exception: they drift through everything and can only be struck on lit ground, or in the moment they materialize to attack.
Two ways around the tier rule. Scrolls from the Altar (select one, tap open ground) hit every monster near the tapped tile whatever its tier: Ember Burst burns, Frost Snap freezes. Ancient weapons found in world chests hit like iron gear but break after a few dozen swings. Neither touches a ghost that is still phased.
Somewhere near your camp, glowing stairs lead down. Underground it is always dark, there is no grass (bring fiber for torches!), ores are richer and monsters are meaner, and every level hides another stairway further down. Each depth has a fragile forward camp beside its stairs up: lose any campfire and that run is over. The surface teaches you the rules; the depths ask if you learned them.
The campfire is your heart: it lights the start, it is what monsters march on, and its death ends the run. Tap it to craft basics, repair, and upgrade. Later, scaffold squares plus a hammer raise real buildings: a workbench for stone gear, a forge for iron gear, a watchtower that lights far and fires at every monster it sees, an altar that weaves monster essence into scrolls. Buildings can be damaged and repaired; hold the hammer on one for three seconds to tear it down. Everything you build is something the night can take away.
Once the campfire reaches level 2 you can build stone walls. Place a chain of scaffolds and tap any of them with the hammer: the whole connected run becomes wall in one swing, as far as your stone lasts. Monsters cannot cross a wall, so they attack it instead; walls have hit points like any building. Enclose an area of dug ground completely and its floor turns to cobblestone: a sanctuary. Nothing spawns inside a sanctuary, ever. Leave one gap in the ring, or one unmined block inside it, and it is just a yard. Ghosts drift straight over walls; only light stops them.
20 slots, stacks of 50, drag & drop everywhere, or tap an item while a chest is open to move it across instantly. Tools are items with durability; recipes are repeatable, so breaking a pickaxe is a setback, not a disaster. The starting wooden pickaxe never breaks: you can always dig your way back.