- The museum has visitors. A crowd gathers behind velvet ropes on both sides of the hall, murmuring, and grows with your collection's fame, up to 38 people in nine looks. Soft dust drifts over the exhibits and the hall fades into darkness at its edges.

- Twelve one-of-a-kind artifacts to dig for, given up in a set order from the forgiving pieces to the ones that punish a careless swing: the Rosewood Casket, the Seer's Eye, the Sun Urn, the Surveyor's Scarab, the Coiled Jade Dragon, the Zephyr, the Celestial Egg, the Warden's Aegis, the Gilded Ammonite, the Regent's Crown, the Laughing King's Mask and the Oracle's Knot. Every piece draws its own crowd, the deepest showpieces most of all, and every piece shows its knocks: chip it in the dig and it comes home visibly cracked.

- The Warden's Aegis: wear it on your back and, once per round, it saves you from the boulder, shoving you clear in a burst of dust and knocking the boulder back. Its amber heart glows while the save is ready.

- The Surveyor's Scarab: carry it and it senses what is coming. Its antennae lift as the next danger nears, a mark over your head names it with a pictogram and fills as you close, and the piece on your back lights along its shell. It is the only thing that warns you about bad ground.

- Combination traps, from your third exhibit onward, one new arrangement with each exhibit after that, each set tight so the second trap lands where the first puts you down: a pendulum over a pit, a pendulum where the collapsing floor leaves you, two pendulums swinging out of step, rocks on a pit's take-off, a beam to crouch under the moment you land a jump, a rockfall beside a breakable floor whose rubble half blocks the way out of the pit, a pendulum swinging across a stone door's opening, a breakable floor right past a door, and a jump beam with a pit a stride after it.

- The fallen beam: a stone beam across the tunnel at chest height. You cannot run through it or jump it, so crouch under it. On the run home the boulder smashes through and barely breaks stride.

- The sliding stone door: carved slabs in a stone frame. Tap E beside a slab to slide it into its wall on the way in. On the run home tap E to pull a slab back across behind you. The boulder has to smash through, and shutting it buys you a moment.

- Bad ground, deep in the tunnels: straight stretches that have come down before, with broken props, spilled rock and someone's dropped lantern. Old beams lie flat along the wall in their posts and swing out across your path as you reach them. Duck the high ones, jump the low ones. The post's height is your only warning, and not every post still has a beam in it. Shallower rock gets a gentler version first, growing from one beam to three as your collection grows.

- Slide: press crouch while running to drop into a slide that carries your speed. You steer less while sliding, dust and grit kick up behind you, and a piece you are carrying goes out in your leading hand. C crouches as well as Ctrl.

- The rock changes as you go deeper. Bring three exhibits home and the tunnel turns to grey limestone under cooler light. Deeper still it is basalt: near-black, tight-fractured, with sparse teal mineral in the walls and the hazard lights turning cold against your warm lantern.

- Hazards on the way out now cost you. Take a hit before the dig and one of your lantern's four panes breaks, the flame gutters, and you walk on by less light. Something up the corridor answers every hit, and when you arrive the dig face shows the knocks you took: the wall gives up sooner.

- At the dig you hold your lantern up and it follows where you are digging.

- Your museum is saved between sessions. Close the game and come back to the same exhibits, scars, visitor count and round. Quitting during a round counts it as lost, along with anything you carried out.

- The closing bell beside the tunnel arch ends a run: ring it, ring it again, and the bell tolls, the hall hears what the run drew, the door shuts, and a new museum opens.

- An artifact you fail to bring home is not lost. The dig offers the same piece again next round in a fresh tunnel, at the condition you left it in, and the boulder that caught you takes its own share out of it. It never comes back worse than poor.

- The run ends when the last plinth is filled, not after a fixed twelve rounds, so losing a round costs you a round instead of the finish.

- The end-of-round summary finishes with what is ahead: the piece you dropped and whether it went down worse, the plinths still empty, and any tool waiting on its plinth.

- Eight achievements: your first find, a piece on display, one brought home pristine, a clean run home, one more round, a tool carried out, five plinths filled, and a crowd of 1,000.

- Hold the right mouse button on the way out to swing the camera around you. It settles back behind you when you let go.

- Sounds: gravel footsteps and a landing crunch in the tunnel, the pendulum's whoosh, a slab crumbling under your foot, harder rock impacts, the crowd's murmur, a scrape that travels with your slide, and a real door closing on the museum.