System mechanic — not covered elsewhere

Digging

Underground is solid rock. You may only ever be inside the volume you've actually dug — and it stays dug forever

Equip a Mining Drill, hold [F] in the open underground, and the game carves a real, permanent tunnel out of solid rock around you — one that has physical walls, is visible from the inside, and is saved to your character forever. This isn't a cosmetic effect: below the surface, the only space you can actually stand in is space you or someone else has personally dug.

The three drills

Each activation carves out a full sphere of rock at that radius around the point you're aiming at, so a Cathedral Bore clears out roughly eight times the volume of a base Mining Drill in one hold of the key. Digging the same pocket of rock repeatedly costs nothing extra — a cell that's already open simply stays open, so standing in one place holding the key down doesn't make your save grow without bound.

It stays dug, and it's shared

Every cell you carve is recorded permanently against your character, cell by cell, rather than as a path you walked while boring. That makes tunnels genuinely persistent rather than a temporary effect, and it also makes them naturally safe for multiplayer: two people digging into the same rock from different directions simply combine what they've each opened up, and neither one's work can undo the other's.

Real walls, not an invisible floor

Before this system existed, the underground had no real boundaries at all — the only thing holding a player up was a single invisible floor plane, with nothing stopping sideways movement through solid rock, dungeon walls, or the edge of the world itself. That's exactly why players could end up walking through walls, clipping out of bounds, or getting stuck inside the floor while drilling. The fix inverts the rule entirely: underground is solid by default, and a tunnel is physical precisely because being inside one is now a fact the game actually checks, the same way a player's own build pieces already blocked movement above ground.

The rule is deliberately one-directional: it only ever stops a move that would leave dug space from inside it. Anywhere the game doesn't track as "dug" at all — an old save from before this system existed, a dungeon interior, Hell, or the hollow Moon — is left completely alone, so nobody who was never inside a tunnel can end up trapped by a rule meant to protect people who are.

You can see what you've dug

A tunnel's walls are actually drawn, textured in stone, from the inside — added specifically because an invisible-but-solid tunnel is indistinguishable from a bug: being stopped by empty-looking air reads as broken collision, not as a wall. Only the outer boundary of dug space is ever rendered — a face is drawn only where a carved cell borders rock that hasn't been carved — so a long corridor costs roughly its surface, not its full volume, and the deeper and longer a tunnel gets, the cheaper that ratio becomes. Tunnel geometry is only kept loaded near you and is fully discarded once you move away, so an hour spent drilling doesn't mean carrying every metre of it in memory for the rest of the session.

Where a drill actually works

Drilling only functions in the true open underground — dungeons, building interiors, shops, the chapel, and the casino all refuse it, along with most off-world locations, since none of those are spaces this system tracks as diggable rock. The one deliberate exception is the surface of the Moon, which has its own separate working use for a drill.

Dig deep enough and you reach Hell

Straight down is a real destination: pass 1,000m of depth and the game breaches you straight through the floor of the world into Hell, with a plain warning the moment it happens. Climbing back above roughly 960m returns you to the ordinary underground. This isn't a hidden or half-built feature — it's exactly the "digging a hole to hell" scenario named in the original request for the drill, and it worked before the rest of this page's own tunnel-collision fixes did.

Version history

• Digging made physically real. Drilling had always moved the camera through rock to simulate boring a tunnel, but the underground had no actual collision to back it up — the only thing holding a player up was a single invisible floor plane, with nothing stopping sideways movement through solid rock, dungeon walls, or the edge of the world itself. That gap was reported as several separate bugs (going out of bounds while drilling, walking through walls underground, getting stuck in dungeon floors), which all turned out to be the same missing rule. Fixed by inverting it entirely: underground is solid rock by default, and a tunnel is physical precisely because being inside one is now a fact the game actually checks.
• Tunnels made visible, so a correctly working tunnel and a movement bug no longer looked identical to a player standing inside one.
• Enemies bound to tunnels too. A creature that's ended up inside a dug tunnel with you can no longer walk straight through its walls the way it could walk through open-world scenery — the rock stops it exactly as it stops the player, so a fight inside a tunnel can't be sidestepped by an enemy simply clipping past a corner.
• The drill learned to explain itself. Trying to drill somewhere it doesn't work — a dungeon, a shop, most off-world locations — used to return the exact same message every other tool gets there ("equip a weapon — there is nothing here to harvest"), which never mentions the drill at all and reads as the tool being broken rather than simply refused. The drill now explains specifically why it won't work in your current location.
• Fixed the drill going completely silent for characters with a bound spell. The drill's activation key is also one of the game's six spellcasting keys, and a spell bound to that same key would silently intercept it — a player holding a drill and pressing the key would simply cast a spell that missed, with no message at all, making the drill look totally unresponsive rather than refused. The drill's own key now takes priority over spellcasting whenever a drill tool is actually equipped, regardless of which of the three drills it is.
• Fixed boring level. Aiming straight ahead used to fall through to the same downward carve angle as looking down, which meant a tunnel driven "level" into a mountainside actually dropped over three metres with every press — the drill could carve a staircase but not a flat floor. Boring level now genuinely holds depth, which is what actually made it possible to carve a real, walkable room rather than only a sloped shaft.

Trivia

• The drill's activation key is checked by asking "is a drill actually in my hand" rather than by matching a specific item's name, which is exactly what lets all three drill tiers share the same fixes without the game needing to know about each one individually.
• The Mining Drill also has an unrelated, required role at the Moon's crater as key equipment for reaching the Hollow — a separate use for the same tool, not covered on this page.