Boulders

A boulder sits in place looking like scenery until something disturbs it. Take away the support underneath, break what it was resting on, or in a few cases just hit it, and it starts rolling. From that moment it travels until a wall stops it, damaging everything in its path along the way.

The word doing the work there is everything. A rolling boulder does not distinguish between you and the things trying to kill you, which is why it cuts both ways. The ones generation places are there to catch you out. The ones you place yourself are one of the few genuinely effective ways to deal with a crowd, and they will damage a boss.

Plain gray is the default, but generation runs a short priority chain before it settles for one, and each step is only checked if the step above it failed. It is the reason boulder types cluster by region rather than appearing evenly.

• Within about eighty tiles of spider wall, half of them come out as Spider Boulders.
• Otherwise, on the dungeon's half of the world and within a thousand tiles of dungeon wall, one in six becomes a Ghoulder.
• Otherwise, within sixty tiles of lava, a third become Lava Boulders.
• Otherwise the secret seeds get their say, which is where poo boulders and the higher rainbow and bouncy rates come from.
• Otherwise a small share are Rainbow or Bouncy Boulders anyway, at roughly one in twenty five and one in twenty.
• Otherwise, if the world has not yet met its quota of friendly boulders, it places one of those instead.

No Traps rewrites the table hardest and does not do what the name promises. Every boulder near a spider nest becomes a spider boulder rather than half of them, ghoulder and lava boulder odds rise by half again, bouncy boulders jump from one in twenty to one in three, poo boulders enter the pool, and the friendly boulder quota doubles. Not the Bees and Truck Stop also bring poo boulders in. Celebration Mk 10 raises rainbow boulders to one in seven and bouncy ones to one in three.

Read the other way, the variant you run into tells you where you are. A spider boulder means spider walls nearby. A ghoulder means you are on the dungeon's side of the world and closer to it than you might have thought. A lava boulder means lava within a screen or two, whether or not you can see any.

Not all of them want you dead. Generation reserves a couple of slots per world for Friendly Boulders: two on a small world, four on medium, six on large, doubled again under No Traps. They are pets rather than hazards.

Because they sit at the bottom of that priority chain, they are the first thing squeezed out. A world dense with spider nests, lava or dungeon proximity spends its boulder budget elsewhere, so a quiet world is a better place to go looking for one.

Boulders can be picked up and placed, and a Boulder Statue produces them from a wire signal, which is the version that scales into a farm. The standard build is a plate or a timer over a corridor that enemies have to walk down. Since a boulder keeps rolling through everything it touches, one that starts in the right place clears far more than a single hit.

Scaled down versions turn up as projectiles from a handful of weapons, the Staff of Earth being the obvious one. And if you want the look without the hazard, Boulder Block is a normal building material with a full furniture set built from it.