[mnaimfaizy]

What changes

Endless code no longer freezes the tab when Trace is off. Untraced code is rewritten only to count loop turns and function calls. Past 1,000,000 the run ends with: "Stopped after 1,000,000 loop turns and calls: a loop or recursion probably does not end. Turn Trace on to watch it step by step." The learner's own try/catch/finally cannot swallow the stop, lines keep their numbers, and callbacks and code after await are counted too. There is no setting for the limit.

Stop really stops. The sandbox iframe is discarded and replaced on Stop, on the host's timeout, and when a new run starts over an old one. Before, Stop changed nothing and a stuck sandbox stayed stuck.

Two dead settings are removed: Timeout and Animations were read by nothing. Stored settings that still hold them load as before. Font size and word wrap stay.

The heap draws up to 20 objects in 2D (it was 9), and 9 in 3D. A step that fits 2D but not 3D is shown in 2D with the line "This step is too large for 3D, so it is shown in 2D"; steps that fit go back to 3D and the choice of 3D is kept. On floors larger than 2×2, reference arrows run along the gutters between cards. Story layouts are unchanged.

Choosing 3D widens a narrow lens pane to the 3D minimum, once, at the moment of switching. It keeps 320px for the editor and 240px for the side pane, and does nothing when the window has no room.

A middle frame in 3D shows two slots and "+N more", with the slots in focus first. It used to show one line cut off.

docs/Playground-Developer-Guide.md is brought in line with the code.

Checks

npx tsc -b, npm run lint, npm run test:run (1,250 tests in 94 files) and npm run build pass; three.js is not in the entry graph. This branch was also merged locally with the content and visual polish PRs: no conflicts, and all checks pass on the combined tree.

Checked in the browser:

• Trace off: while (true) {} stops with the message; a loop inside try/catch/finally prints nothing from either block; an endless await loop stops after the synchronous code finishes; a normal loop with a timer runs as before; an error still reports the learner's line.
• A 15-node linked list draws in 2D. In 3D its last step falls back to 2D with the line, and an earlier step with two objects is drawn in 3D.
• At 1440px, switching to 3D widens the lens pane to about 773px.
• A recursion with three parameters shows "a: 3 b: 'x' +1 more" on its middle frame.
• Settings lists only Font Size and Word Wrap.
• Stop during a running interval, then a new run, works.

Limits that remain

• The guard cannot stop one long built-in call ('x'.repeat(...), a regular expression that backtracks) or code built with eval or new Function.
• Endless recursion is usually ended by the engine's own stack limit first.
• Stop cannot interrupt a synchronous loop in a browser that runs the iframe on the page's thread; the guard is what covers that case.
• A 15-node tree is dense with arrows. They are tested not to cross cards, but were not judged by eye for every shape.

🤖 Generated with Claude Code