Every interaction a human can have with software falls into three classes: spatial (arranging things in space), continuous (manipulating something that evolves), and stepwise (moving through a structured process). These three islands prove one deterministic, reversible, dependency-free substrate expresses all of them. The same op-log runtime drives each: state is a pure projection of an operation log, so undo is exact, replay is byte-identical, and every gesture is inspectable.
No frameworks, no network, no build step. Drag, step, advance — then watch the inspector. Undo reproduces an earlier state exactly; Verify confirms replay matches the live state.
Spatial interaction. A seeded force layout (same graph + seed → identical positions, no animation jitter). Click to select, drag to move (a recorded, reversible op). This is the shape of a lineage DAG, a dependency map, a corridor mesh.
Continuous interaction + geometric computation. The "simulation" applies a rotor — a real 2D rotation — to every point each tick. Twelve 30° steps complete a full turn and return to the origin exactly (a rotor round-trip). Click the canvas to add a point; step forward and back.
Stepwise interaction. A deterministic state machine; each advance records its input as an op, so "back" is just undo on the log — no framework, no special undo stack. This is the shape of the Lab embryology, a compliance ritual, any multi-phase form.