Mirror
What you do on one side happens on the other side too. Symmetry without bookkeeping.
Mirror builds both halves at once. Toggle it on and whatever you do on one side happens on the other: nudge a ring, grow an ear Out , cut a Slice , and each lands on both sides as one undo step.
The axis chip
While Mirror is on, a word chip sits beside the toggle showing which way the mirror faces: ↔ left–right, ⤢ front–back, or ↕ up–down. Tap the chip to cycle. Left–right is the one you want for faces and bodies.
What it does and doesn’t touch
Mirror reflects your edits. It doesn’t mirror placing new pieces in Stack, and it doesn’t retroactively symmetrize a model; it keeps a symmetric model symmetric while you work. Each piece’s mirror plane runs through where it was stamped, so the plane never drifts as the model grows.
When the other side has no matching spot (the model is already asymmetric there), the edit applies to your side only and the app says so. Shapes drawn on round surfaces also sit out for now; the hint tells you when.