Place walls: Pick an element, then click the grid lines (edges) — walls sit on edges so they connect at corners for L-shapes and rooms.

Foundation / Dig / Rebar: These snap to grid cells. Use level −1 for below-ground foundation and excavation.

Stacking: Switch floor level (G, 1, 2, 3) to build upward. Walls stack per floor.

Windows & Doors: Pick "Window Wall" or "Doorway" and place like a wall — they show the opening.

See underground: Tap 👁 Floor to make the ground transparent and view foundations below.

Save your work: 💾 Save stores the build in this browser. 📂 Load brings it back.