whatA wavepacket in a box -- and no integrator at all: the packet is expanded once in the box's own eigenmodes and every later instant is computed EXACTLY from their phases; the only error is the truncated tail of the expansion, posted in the HUD. Each row of the image is |psi(x,t)|, woven downward from t = 0 to one full revival time.

whyThe claim: structure, not mush. A quantum packet in a box does not smear into noise -- the phases, with energies proportional to n squared, conspire. Diagonal threads cross the carpet where the packet's copies race the walls; at T/2 it reassembles perfectly at the mirrored position (fidelity measured to the digit); at T/4 it stands as ghost copies of itself; and at the bottom edge it returns home exactly -- the full revival. The same arithmetic underlies the Talbot effect in optics.

howSpectral evolution in 64 modes; revival, mirror, and fractional fidelities are computed from the mode weights, not read off pixels. Click to launch a new packet -- your x is its home, your height its speed -- and weave the next carpet. The print renders the weave as threads whose width follows the amplitude. One integer seeds the loom.