The Toggling Switch Gate chip has been redesigned to be faithful to the circuit it packages: ports now sit where the w2l1 Gatekeeper construction puts them (control rail straight across the top, inputs west, outputs east, in the Dup/rDup form factor) — and every World 2 level was rebuilt around it, then play-tested end to end.
Highlights
- The Duplicator (W2·L4), redesigned. The #1 play-tester friction point is gone: the pre-placed switch gates spread into a centered column, timing margins are generous (a first-try natural wiring certifies), and the layout is honest — gate A is mounted upside-down so the copy loop runs dead straight, leaving exactly ONE forced wire crossing, bridged by the one Crossover you're handed.
- World 2 planarity. The Sorting Office, Merge Lanes, AND Finally, and Putting It Together all route with zero crossings now; Merge Lanes visibly IS the demultiplexer mirror-imaged ("run it in reverse", literally — and the post-level text now invites you to watch it happen with the ◀ Reverse button).
- Looser schedules, measured. Pulse-injection times on W2·L4/L6 were re-spaced using a new timing-margin instrument in the engine; the capstone now tolerates several extra cells of wire on every path.
- Fairness & polish guards in the test suite: minimum I/O spacing (readable labels), no labels pushed off the board edge, references must place-and-use every supplied component, and a hard timing-margin floor for every reference across all 100 certification seeds — plus the planarity counter now catches a wire crossing itself.
- Attribution & pedagogy: Andrew Ressler is credited alongside Feynman where switch gates are introduced (his 1981 MIT thesis proved them universal; the two inventions were independent); the TCB is named in full (Toggling Controlled Barrier); and several level texts were tightened — the W2·L6 garbage accounting is now exact, and its universality claim is properly scoped to the {Rotary, TCB} element set.
Full change detail in CLAUDE.md's changelog and TODO.md. Test suite: 586 + 196 checks green.