Build: with the Build tool, left-click the floor grid to drop a block, or click a face of a block to stack another. An outline shows where it will land before you click. Erase removes the block under the cursor; Paint recolours it.

Box fill (X): click two opposite corners to fill a whole rectangular volume with the active colour. Pick (K) grabs the colour of the block you click.

Select (V): click two corners to mark a region. Then arrow keys move it in X/Z, PageUp/Dn in Y, Del clears it, Ctrl+D duplicates, Esc deselects — or use the Fill/Clear/Duplicate buttons.

Colour: pick a swatch — new blocks use it. Preset loads a ready-made colour set; edit the active swatch with the colour picker or a #hex, and press + to add your own (up to 64).

Layers: the Layer stepper (or [ / ]) sets the active height. Build and Box fill always place on that layer, so pick layer 0 for the floor, raise it to stack a layer on top. Mirror X mirrors every edit for symmetric models.

Camera: right-drag to orbit, scroll to zoom in and out, arrow keys to move up/down and sideways, middle-drag to pan. On touch, one finger orbits and two fingers pinch to zoom. Fit frames the model; Reset (R) recentres.

Tools & history: B build, E erase, P paint. Ctrl+Z / Ctrl+Shift+Z undo/redo. Work autosaves to this browser. Grid sets the build volume (1–64); New clears it.

Export: STL is a solid, watertight mesh for slicing and printing — one voxel is 10 mm, oriented Z-up. OBJ and glTF open in 3D viewers (glTF keeps colour; STL and OBJ are shape only). PNG saves a snapshot of the current view; GIF records a spinning turntable. Save keeps the whole model as a .json; Load reopens one — loaded files are validated and nothing from them is ever run.