Model: i∂ψ/∂t = [-½∇² + V]ψ (ℏ=m=1) on a 128×128 grid, solved by the split-step Fourier method (Strang splitting, unitary). Height = |ψ|², colour = phase. Tunnelling reference: T = [1 + V₀²sinh²(κa)/(4E(V₀-E))]⁻¹. Absorbing borders remove outgoing waves.