Phase 5 — Execute (Iteration 2)

Phase 5 — Execute (Iteration 2)

What was built

Study Mode added to iteration-2/pathfinding-race.html (evolved from the v1 baseline; v1 left intact). The 4-up race is unchanged and remains the default view. A 📖 Study / Pseudocode toggle (default off) opens a focused, line-by-line pseudocode tracer for one algorithm.

New pieces, per the plan's build sequence:

  1. Engine refactor — makeSearch is now a generator micro-stepper; step() is the expansion-boundary driver (race), microStep() yields one pseudocode line (study).
  2. Teaching/pseudocode data — shared skeleton (10 lines), per-mode annotations for the three divergent lines (pop/cost/improve), narration templates, per-algorithm blurbs, comparison table.
  3. Study view — focused larger grid, pseudocode list, narration bar, thumbnails, comparison table; built once via DOM APIs (textContent, no innerHTML).
  4. Study controller — mode routing (race|study); micro-step → active-line highlight + grid cursors (node expanded / neighbor inspected) + overlay accumulation + live narration; focus switching; Play auto-advances lines at the speed slider.
  5. Difference-highlighting — divergent lines flagged and annotated for the focused algorithm; comparison table highlights the focused row.

Step 1 regression gate (the critical one)

After refactoring the engine to the generator, the entire iteration-1 suite was re-run against the refactored file and passed identically — same race outcome (cost 44/36/44/36, visited 319/417/21/261, same statuses), 42 engine assertions, 8 static checks, 20 integration assertions. The race controller was not modified; it consumed the new step() transparently. Only after this gate did study mode get built.

Tests (all green) — saved under iteration-2/tests/

Suite Scope Result
trace_proto.js generator vs iteration-1 engine oracle (4 algos × 3 fixtures) 14/14
v2_verify.js inlined refactored engine + static security/offline scan 42/42 + 8/8
v2_integration.js race mode unchanged (build, paint, race, step, reset, no-path) 20/20
v2_study.js study toggle, scaffold, line-by-line PC, grid sync, annotations, full study run, no-path-in-study, race-after-study 26/26

Total: 110 assertions passing. Study line trace confirmed: init → pop → goal → mark → for → cost → improve → push.

Bugs found and fixed

Acceptance criteria results (vs. plan checklist)

# Criterion Result
1 Race mode unchanged (regression) PASS — 20/20 identical race results
2 Study toggle default OFF; initial view identical to v1 PASS — study tests
3 Entering study focuses one; switch via thumbnails or panel click PASS for toggle + thumbnails; panel-title click wired, not auto-asserted → Verify
4 Shared skeleton shown; active line advances PASS — sequence asserted
5 Study Step = one line; Play auto-advances PASS
6 Focused grid: node + neighbor cursors; accumulates overlays PASS for overlays (closed/open asserted); cursor classes implemented, not explicitly asserted → Verify
7 Live plain-English narration with values PASS — populated; no-path narration asserted
8 Divergent annotations per algo; switching updates PASS — A*→BFS swap asserted
9 Teaching blurb + comparison table PASS for table; blurb set on focus, text not asserted → Verify
10 No-path in study graceful PASS — status "no path", narration "unreachable"
11 Generator race reproduces iteration-1 results exactly PASS — oracle + identical race
12 No innerHTML/eval/fetch/external URLs PASS — 8/8 static

Honest handoff to Verify

All testable-without-a-browser behavior is green, including a full regression of iteration 1. What a headless run can't fully judge — visual rendering of the study layout, the active-line and cursor highlighting as seen, panel-title click entry, blurb/table legibility, the feel of line auto-play, and reading the narration in context — are flagged above for the adversarial Verify pass and a human look.