Precision & modifiers

Toggles and filters that change where and how the building tools write. They apply on top of whichever tool is active.

Masking

The Mask section of the right dock (open it from its dock tab, or click the Mask chip in the options bar while a mask is active) limits where the painting tools — build, erase, brush, fill, line, and shape — are allowed to write. Turn it on, pick a Preset to set up a common mask in one click (surface only, underground, exposed to sky, replace active block, empty cells), or use the + Add condition menu to build your own — a condition's controls appear only while it's in use, and its ✕ removes it again:

Block is — the existing block must match one you've added (use + Active block). Great for "only replace stone".
Material is — any form of a material (e.g. all oak planks/stairs/slabs).
Biome is — add the biome under the camera with + Current biome.
Adjacent to — a face-neighbour must match (e.g. only next to water).
Height (Y range) — only between a min and/or max Y.
Cell — require the cell to be solid or empty.
Exposed to sky / Surface only — open to the sky / topmost solid of a column.

The Advanced fold (closed by default) holds the rest: choose Match all (every condition) or Match any (at least one), optionally Invert to write everywhere except the match, and the expression field. Structural operations — paste, move / clone, and stamp — ignore the mask so explicit placements always land.

While the mask is on, a Mask chip in the options bar shows its summary — click the chip to reopen this section, or its ✕ to switch the mask off. If a stroke is mostly filtered away by the mask, the chip pulses briefly — that's your cue why the brush barely painted.

Expression (advanced): prefer typing? The expression field in the Advanced fold takes a mask directly, for example block:stone and y<64 and sky. Combine terms with and / or / not (and parentheses); terms are block:, material:, biome:, adjacent: (comma-separated lists), height as y<64 / y>=0 / y=10 / y:0..64, and the flags sky, surface, solid, air. From builder fills the field from the controls above so you can fine-tune it.

Symmetry

Mirror your edits live across the X / Y / Z planes (up to 8-fold), or use Radial symmetry (2- or 4-fold) to rotate them around a vertical axis. Set the centre by clicking a block. Configure it in the dock's Symmetry section (its dock tab, or M); while any mirroring is on, a Mirror chip in the options bar shows the active planes — click it to reopen the section, or its ✕ to switch mirroring off. Symmetry applies to build, erase, brush, line, and the Shape tool, and undoes as one step.

Orient placement

The Orient toggle (in the cluster of placement toggles at the right end of the options bar; on by default) makes blocks face the way you place them, like Minecraft itself:

Facing — stairs, trapdoors, chests, furnaces, observers and droppers face the direction you're looking; torches, ladders, buttons, levers, wall signs and banners attach to the wall (or floor) you click.
Axis — logs and other pillar blocks align to the face you click (clicking the top gives an upright log, a side gives a horizontal one).
Halves — stairs and slabs go in the top or bottom of the cell depending on where on the face you click.
Multi-block — doors and beds place their second half automatically; erasing either half removes both.
Rails — placed rails curve and slope to connect to neighbouring rails, and extending a track re-routes the rails it joins.

Turn it off (its options-bar toggle, or bind a key under Settings → Shortcuts) to place blocks in their raw default orientation. Picking an exact variant with the Eyedropper always places it as-is, regardless of this toggle.

Snap (contiguous lines)

The Snap toggle in the options bar (off by default) keeps drags and lines contiguous — orthogonal, with 90° corners and no diagonal gaps. It works for any block, which is especially handy for fences, walls, glass panes, iron bars, and rails, since those only join orthogonal neighbours.

Build drag stays connected as you draw: the cursor is rubber-banded to the last block so a fast or diagonal drag fills in 90° corners instead of leaving gaps — draw freely and the run is always contiguous.
Line tool routes orthogonally between waypoints (contiguous 90° corners) instead of drawing a diagonal/curved line.
Rails curve and slope at the corners automatically, so a snapped L of rails becomes a proper curved track; fences/walls/panes connect along the run.

Turn it off (its options-bar toggle, or a key under Settings → Shortcuts) for free-hand drawing where diagonals are allowed.

Auto-waterlog

The Waterlog toggle in the options bar (off by default) keeps water around the blocks you place, the way Minecraft waterlogs them:

Placing a waterloggable block into water — fences, slabs, stairs, walls, glass panes and bars, trapdoors, signs, ladders, lanterns, chains, chests, campfires, leaves, rails, and similar non-full blocks — keeps the cell's water instead of clearing it, so the block reads as submerged and exports waterlogged.
Placing water onto such a block waterlogs it (the block stays, water fills its cell) rather than replacing the block with a plain water block.

The block list matches Minecraft's exactly, so blocks the game won't waterlog — full cubes like stone and dirt, and also doors and fence gates — displace the water instead, as in-game. The modifier is fully undoable, and submerged-only plants (kelp, seagrass, coral) stay watered automatically whether or not it's on.

Structures carry their water with them: copying, pasting, rotating, flipping, saving to your library and stamping all keep waterlogged blocks wet, and generated structures that stand in water — sunken shipwrecks, ocean ruins, village walkways — come out waterlogged the way Minecraft generates them.