feuerwerk/tools/e2e/41-physics.mjs

import { edge, node } from '../lib/builders.mjs';
import { inView, LANES, MAKE_OBJECT } from './lib/scaffold.mjs';

/** Kicks its owner in On start, with the scene's gravity switched off first: it glides at 100 per second. */
const KICK = 200;
const KICKED_MASS = 2;
const kickGraph = {
  nodes: [
    node('pk-start', 'OnStart', 0, 0),
    node('pk-gravity', 'SetGravity', 300, 0, { x: 0, y: 0 }),
    node('pk-owner', 'Owner', 300, 160),
    node('pk-kick', 'ApplyImpulse', 600, 0, { x: KICK, y: 0 }),
  ],
  edges: [
    edge('pk-e1', 'pk-start', 'exec', 'pk-gravity', 'exec'),
    edge('pk-e2', 'pk-gravity', 'exec', 'pk-kick', 'exec'),
    edge('pk-e3', 'pk-owner', 'object', 'pk-kick', 'object'),
  ],
};

/** Walks its owner right at 120 per second with "Collide with solids" on. */
const WALK = 120;
const walkGraph = {
  nodes: [
    node('pw-update', 'OnUpdate', 0, 0),
    node('pw-owner', 'Owner', 0, 160),
    node('pw-move', 'Move', 300, 0, { dx: 1, scale: WALK, collide: true }),
  ],
  edges: [
    edge('pw-e1', 'pw-update', 'exec', 'pw-move', 'exec'),
    edge('pw-e2', 'pw-update', 'dt', 'pw-move', 'dt'),
    edge('pw-e3', 'pw-owner', 'object', 'pw-move', 'object'),
  ],
};

/**
 * Rolls its owner right at 120 per second with "Collide with solids" on, and logs Move's normal
 * (x, then y) on every frame that hits something.
 */
const BALL_R = 20;
const CORNER_DROP = 12;
const rollGraph = {
  nodes: [
    node('pr-update', 'OnUpdate', 0, 0),
    node('pr-owner', 'Owner', 0, 160),
    node('pr-move', 'Move', 300, 0, { dx: 1, scale: WALK, collide: true }),
    node('pr-hit', 'Branch', 600, 0),
    node('pr-log-x', 'Log', 850, 0),
    node('pr-log-y', 'Log', 1100, 0),
  ],
  edges: [
    edge('pr-e1', 'pr-update', 'exec', 'pr-move', 'exec'),
    edge('pr-e2', 'pr-update', 'dt', 'pr-move', 'dt'),
    edge('pr-e3', 'pr-owner', 'object', 'pr-move', 'object'),
    edge('pr-e4', 'pr-move', 'exec', 'pr-hit', 'exec'),
    edge('pr-e5', 'pr-move', 'hit', 'pr-hit', 'condition'),
    edge('pr-e6', 'pr-hit', 'then', 'pr-log-x', 'exec'),
    edge('pr-e7', 'pr-move', 'normalX', 'pr-log-x', 'message'),
    edge('pr-e8', 'pr-log-x', 'exec', 'pr-log-y', 'exec'),
    edge('pr-e9', 'pr-move', 'normalY', 'pr-log-y', 'message'),
  ],
};

/**
 * The physics engine (Rapier) loads in the editor, in the background after the first project is
 * open, from a chunk of its own – the editor bundle does not carry it. A played scene simulates its
 * rigidbodies on it (#146).
 */
export async function physics(t) {
  const { check, json, waitUntil, consoleLog, evaluate, mutate, select, click, clickText, press, typeText } =
    t;
  const { has, object, asset, objects, state, settle, sleep, play, stop, shot, mouse, showTab } = t;
  const { drag, undo } = t;

  await waitUntil(`['ready', 'failed'].includes(__gm.physics().state)`, { timeout: 15000 });
  const status = await json('__gm.physics()');
  check(
    'Rapier loads in the editor without Play',
    status.state === 'ready' && status.version === '0.20.0',
    JSON.stringify(status),
  );
  const scripts = await json(
    `performance.getEntriesByType('resource').map((e) => e.name).filter((n) => n.endsWith('.js')).map((n) => n.split('/').pop())`,
  );
  check(
    'it comes from a chunk of its own',
    scripts.some((name) => /^rapier-.+\.js$/.test(name)),
    JSON.stringify(scripts),
  );
  check(
    'loading it writes nothing to the console',
    !consoleLog.some((line) => /\[physics\]|rapier/i.test(line)),
    consoleLog.filter((line) => /\[physics\]|rapier/i.test(line)).join(' | '),
  );

  // 41b. A crate and a ball above a ground on a lane of their own, each with a collider and no
  //      rigidbody yet. The rigidbodies come from the hierarchy menu, the ball's bounciness is typed
  //      into its collider's field, and the played scene is sampled frame by frame.
  const Y = LANES.physics;
  const REST = Y + 200 - 20 - 20; // the ground's top face minus half of a 40-high body
  await mutate(`
    const scene = __gm.state.activeScene;
    const assets = __gm.state.project.assets;
    ${MAKE_OBJECT}
    const collider = (id, props) =>
      assets.push({ id, type: 'collider', name: id, props: { shape: 'box', width: 40, height: 40, radius: 20, isTrigger: false, ...props } });
    collider('phys-col-ground', { width: 600, height: 40 });
    collider('phys-col-crate', {});
    collider('phys-col-ball', { shape: 'circle' });
    const put = (id, assetId, parentId, x, y, name, overrides = {}) => {
      const o = make(id, assetId, parentId, y, name);
      o.position.x = x;
      o.overrides = overrides;
      scene.objects.push(o);
    };
    put('phys-ground', 'crate', '', 0, ${Y + 200}, 'Physics ground', { width: 600, height: 40 });
    put('phys-crate', 'crate', '', -100, ${Y}, 'Physics crate', { width: 40, height: 40 });
    put('phys-ball', 'crate', '', 100, ${Y}, 'Physics ball', { width: 40, height: 40 });
    put('phys-ground-col', 'phys-col-ground', 'phys-ground', 0, 0);
    put('phys-crate-col', 'phys-col-crate', 'phys-crate', 0, 0);
    put('phys-ball-col', 'phys-col-ball', 'phys-ball', 0, 0);
    __gm.state.select(null)`);
  const selectObject = (id) => select({ kind: 'object', holderId: 'scene1', objectId: id, objectIds: [id] });
  const rigidbodyFromMenu = async (id) => {
    await selectObject(id);
    const row = await inView(t, '__gm.leftColumn().objects', `__gm.hierarchyRow(${JSON.stringify(id)})`);
    const before = (await objects()).length;
    await click(row.x, row.y, 'right');
    await clickText('Add rigidbody…');
    // An enabled entry opens the second menu (#222); a disabled one leaves the first standing.
    if (await has('Create new rigidbody')) await clickText('Create new rigidbody');
    await press('Escape');
    const s = await state();
    const selected = s.selection?.kind === 'object' ? await object(s.selection.objectId) : null;
    return { added: (await objects()).length - before, selected };
  };
  const crate = await rigidbodyFromMenu('phys-crate');
  const crateBody = crate.selected;
  check(
    'Add rigidbody puts a dynamic rigidbody below the object and shows its settings',
    crate.added === 1 &&
      crateBody?.parentId === 'phys-crate' &&
      (await asset(crateBody.assetId))?.type === 'rigidbody' &&
      (await has('Body type')) &&
      (await has('Dynamic')),
    JSON.stringify(crate),
  );
  check(
    'the rigidbody is drawn as an icon in the overlay',
    crateBody && (await evaluate(`__gm.layerOf('${crateBody.id}')`)) === 'overlay',
  );
  const again = await rigidbodyFromMenu('phys-crate');
  check('the menu offers no second rigidbody', again.added === 0, JSON.stringify(again));
  const ballBody = (await rigidbodyFromMenu('phys-ball')).selected;
  await evaluate(`__gm.lookAt(0, ${Y + 100})`);
  await settle();
  await shot('41-rigidbody');
  // Every symbol has an icon and wants its object's position. One with room stands there; icons
  // that want the same spot share it on a ring round it, whoever owns them – two stand left and
  // right of it, in hierarchy order: the seeded collider first, the rigidbody added above second.
  const icons = {
    ground: await json(`__gm.sceneIcon('phys-ground-col')`),
    crate: await json(`__gm.sceneIcon('phys-crate-col')`),
    crateBody: await json(`__gm.sceneIcon('${crateBody?.id}')`),
    ball: await json(`__gm.sceneIcon('phys-ball-col')`),
    ballBody: await json(`__gm.sceneIcon('${ballBody?.id}')`),
  };
  const near = (icon, x, y) =>
    icon?.visible === true && Math.abs(icon.x - x) < 0.01 && Math.abs(icon.y - y) < 0.01;
  check(
    'a symbol with room around it stands on its object, in the overlay',
    near(icons.ground, 0, Y + 200) && icons.ground.layer === 'overlay',
    JSON.stringify(icons.ground),
  );
  check(
    'icons on one spot stand left and right of it, a symbol apart',
    near(icons.crate, -110.5, Y) &&
      near(icons.crateBody, -89.5, Y) &&
      near(icons.ball, 89.5, Y) &&
      near(icons.ballBody, 110.5, Y),
    JSON.stringify(icons),
  );
  // An icon is clicked like its object: it selects it, even over a sprite. Beside the icon the
  // sprite under it is picked as before.
  const selectedId = async () => {
    const s = await state();
    return s.selection?.kind === 'object' ? s.selection.objectId : null;
  };
  const zoom = (icons.crateBody.screen.x - icons.crate.screen.x) / 21;
  const picks = {};
  for (const [name, id, dx] of [
    ['groundIcon', 'phys-ground-col', 0],
    ['crateIcon', 'phys-crate-col', 0],
    ['crateBodyIcon', crateBody?.id, 0],
    ['groundBeside', 'phys-ground-col', 40],
  ]) {
    await select(null);
    const at = await json(`__gm.sceneIcon('${id}')?.screen`);
    await click(at.x + dx * zoom, at.y);
    picks[name] = { selected: await selectedId() };
  }
  check(
    'a click on an icon selects its object, beside it the sprite below',
    icons.ground.clickable === true &&
      picks.groundIcon.selected === 'phys-ground-col' &&
      picks.crateIcon.selected === 'phys-crate-col' &&
      picks.crateBodyIcon.selected === crateBody?.id &&
      picks.groundBeside.selected === 'phys-ground',
    JSON.stringify({ zoom, picks }),
  );

  await selectObject('phys-ball-col');
  const field = await inView(t, '__gm.inspectorRect()', "__gm.inspectorField('Bounciness')");
  if (field) {
    await click(field.x, field.y);
    await press('a', { ctrl: true });
    await typeText('0.8');
    await press('Enter');
  }
  await settle();
  check(
    "the collider's Bounciness field takes 0.8",
    (await object('phys-ball-col'))?.overrides?.bounciness === 0.8,
    JSON.stringify({ field, overrides: (await object('phys-ball-col'))?.overrides }),
  );

  await select(null);
  await play();
  await evaluate(`(() => {
    const out = (window.__physicsSamples = []);
    const start = performance.now();
    const sample = () => {
      const w = __gm.world();
      if (!w) return;
      const y = (id) => w.entities.find((e) => e.objectId === id)?.worldY;
      out.push({ t: performance.now() - start, crate: y('phys-crate'), ball: y('phys-ball') });
      if (performance.now() - start < 3000) requestAnimationFrame(sample);
    };
    requestAnimationFrame(sample);
  })()`);
  await sleep(3300);
  const samples = await json('window.__physicsSamples');
  await stop();

  const last = samples.slice(-20).map((s) => s.crate);
  check(
    'the crate falls onto the ground and stays there',
    samples.length > 100 && samples[0].crate < REST - 50 && last.every((y) => Math.abs(y - REST) < 1),
    JSON.stringify({ frames: samples.length, first: samples[0], last: last.slice(-3), rest: REST }),
  );
  // The heights the ball climbs back to: every turn from rising to falling after the first landing.
  // Turning points, not a threshold at the ground: the ball lands at ~9 px per frame, and whether a
  // drawn frame comes within a pixel of the landing depends on where it falls between two steps.
  const peaks = [];
  let landed = false;
  for (let i = 1; i < samples.length - 1; i++) {
    const [before, y, after] = [samples[i - 1].ball, samples[i].ball, samples[i + 1].ball];
    if (y >= before && y > after) landed = true;
    else if (landed && y <= before && y < after && REST - y > 2) peaks.push(REST - y);
  }
  const drop = REST - Y;
  check(
    'the ball bounces back up and every bounce is lower than the one before',
    peaks.length >= 2 &&
      peaks[0] / drop > 0.4 &&
      peaks[0] / drop < 0.8 &&
      peaks.every((h, i) => i === 0 || h < peaks[i - 1]),
    JSON.stringify({ drop, peaks: peaks.map((h) => Math.round(h * 10) / 10), frames: samples.length }),
  );
  check(
    'playing left the scene as it was',
    (await object('phys-crate'))?.position.y === Y && (await object('phys-ball'))?.position.y === Y,
  );

  // A body dragged in the scene view while the game runs sticks to the pointer as if it had no
  // rigidbody: lifted off the ground it hangs where it is held, and is let go at rest.
  const LIFT = 150;
  await play();
  await sleep(1500);
  await showTab('scene');
  await selectObject('phys-crate');
  await settle();
  const grab = await json(`__gm.objectRect('phys-crate')`);
  const scale = grab.w / 40;
  // Below the middle, where the collider's and the rigidbody's icons are not.
  const from = { x: grab.x, y: grab.y + grab.h * 0.35 };
  const to = { x: from.x, y: from.y - LIFT * scale };
  await mouse('mouseMoved', from.x, from.y);
  await mouse('mousePressed', from.x, from.y, 'left');
  for (let i = 1; i <= 10; i++) {
    await mouse('mouseMoved', from.x, from.y + ((to.y - from.y) * i) / 10, 'left', { buttons: 1 });
    await sleep(16);
  }
  const target = REST - LIFT;
  const crateY = "__gm.world()?.entities.find((e) => e.objectId === 'phys-crate')?.worldY";
  // The last move reaches the body a few frames later: preview, physics step, drawn one step
  // behind. Reading right away raced it and caught the ninth move's height (#282).
  const arrived = await waitUntil(`Math.abs(${crateY} - ${target}) < 1.5`, {
    timeout: 2000,
    label: 'the crate reached the pointer',
  }).then(
    () => true,
    () => false,
  );
  // Every frame recorded in the page, so the count follows the frames and not the round trips.
  // The page also stamps the release itself: a stamp taken after the round trip came frames late,
  // and the first sample after it was already 7 units into the fall on the WSL runner.
  await evaluate(`(() => {
    const out = (window.__dragSamples = []);
    const sample = () => {
      out.push({ t: performance.now(), y: ${crateY} });
      if (!window.__dragSamplesDone) requestAnimationFrame(sample);
    };
    window.__dragSamplesDone = false;
    window.__dragLetGo = undefined;
    window.addEventListener('pointerup', () => (window.__dragLetGo = performance.now()), {
      capture: true,
      once: true,
    });
    requestAnimationFrame(sample);
  })()`);
  await sleep(1000);
  await shot('41-drag-while-playing');
  const dragInfo = { grab, selected: (await state()).selection?.objectId };
  await mouse('mouseReleased', to.x, to.y, 'left');
  await sleep(300);
  await evaluate('window.__dragSamplesDone = true');
  const dragSamples = await json('window.__dragSamples');
  const letGo = await evaluate('window.__dragLetGo');
  const log = (await json('__gm.world()'))?.log ?? [];
  await stop();
  const heldSamples = dragSamples.filter((s) => s.t < letGo);
  const held = heldSamples.map((s) => s.y);
  // How long the hold was watched, not how many frames that took: a busy runner drew 21 frames
  // in the second a quiet one draws 50 in, and a count of 30 called that a failure.
  const heldFor = held.length > 1 ? heldSamples.at(-1).t - heldSamples[0].t : 0;
  const released = dragSamples.filter((s) => s.t >= letGo);
  // 200 ms of free fall from rest is about 25 below the hold, a body let go at speed is not.
  const falling = released.filter((s) => s.t - letGo <= 200).map((s) => s.y);
  const fell = falling.at(-1);
  check(
    'a body dragged while playing hangs where the pointer holds it and is let go at rest',
    arrived &&
      held.length >= 5 &&
      heldFor >= 800 &&
      held.every((y) => Math.abs(y - target) < 1.5) &&
      // Let go it only falls: no jump above the hold, no kick up. How far the first frame after
      // the release has already fallen follows the frame time, so that is not a bound here.
      falling.every((y, i) => y > target - 1.5 && (i === 0 || y >= falling[i - 1] - 0.01)) &&
      fell > target + 1 &&
      fell < target + 40 &&
      !log.some((line) => line.includes('moved directly')),
    JSON.stringify({
      target,
      arrived,
      held: { frames: held.length, ms: Math.round(heldFor), first: held[0], last: held.at(-1) },
      stamped: typeof letGo === 'number',
      released: released.slice(0, 3).map((s) => [Math.round(s.t - letGo), s.y]),
      fell,
      log,
      dragInfo,
    }),
  );

  const bodies = [crateBody?.id, ballBody?.id].filter(Boolean);
  await mutate(`
    const p = __gm.state.project;
    const scene = __gm.state.activeScene;
    const gone = new Set(${JSON.stringify(bodies)});
    const assets = new Set(scene.objects.filter((o) => gone.has(o.id)).map((o) => o.assetId));
    scene.objects = scene.objects.filter((o) => !o.id.startsWith('phys-') && !gone.has(o.id));
    p.assets = p.assets.filter((a) => !a.id.startsWith('phys-col-') && !assets.has(a.id));
    __gm.state.select(null)`);

  // 41c. The graph drives the physics (#147): a crate kicked in On start with gravity switched off
  //      by Set gravity, and a walker whose Move with "Collide with solids" runs into a free crate.
  const hintsBefore = consoleLog.filter((line) => line.includes('[physics]')).length;
  await mutate(`
    const scene = __gm.state.activeScene;
    const p = __gm.state.project;
    const assets = p.assets;
    ${MAKE_OBJECT}
    const behavior = (id, name, graph) => {
      const asset = structuredClone(assets.find((a) => a.id === 'mover'));
      Object.assign(asset, { id, name, props: { enabled: true, runInEditor: false }, variables: [], graph });
      assets.push(asset);
    };
    behavior('phys-kick', 'Physics kick', ${JSON.stringify(kickGraph)});
    behavior('phys-walk', 'Physics walk', ${JSON.stringify(walkGraph)});
    assets.push({ id: 'phys-col-box', type: 'collider', name: 'phys-col-box', props: { shape: 'box', width: 40, height: 40, radius: 20, isTrigger: false } });
    assets.push({ id: 'phys-rb-kicked', type: 'rigidbody', name: 'phys-rb-kicked', props: { bodyType: 'dynamic', mass: ${KICKED_MASS} } });
    assets.push({ id: 'phys-rb-free', type: 'rigidbody', name: 'phys-rb-free', props: { bodyType: 'dynamic', mass: 0 } });
    const put = (id, assetId, parentId, x, y, name, overrides = {}) => {
      const o = make(id, assetId, parentId, y, name);
      o.position.x = x;
      o.overrides = overrides;
      scene.objects.push(o);
    };
    const box = { width: 40, height: 40 };
    put('phys-kicked', 'crate', '', -200, ${Y}, 'Kicked crate', box);
    put('phys-kicked-col', 'phys-col-box', 'phys-kicked', 0, 0);
    put('phys-kicked-rb', 'phys-rb-kicked', 'phys-kicked', 0, 0);
    put('phys-kicked-kick', 'phys-kick', 'phys-kicked', 0, 0);
    put('phys-walker', 'crate', '', 0, ${Y + 100}, 'Walker', box);
    put('phys-walker-col', 'phys-col-box', 'phys-walker', 0, 0);
    put('phys-walker-walk', 'phys-walk', 'phys-walker', 0, 0);
    put('phys-pushed', 'crate', '', 60, ${Y + 100}, 'Pushed crate', box);
    put('phys-pushed-col', 'phys-col-box', 'phys-pushed', 0, 0);
    put('phys-pushed-rb', 'phys-rb-free', 'phys-pushed', 0, 0);
    __gm.state.select(null)`);
  await play();
  // A model event while playing re-reads the scene (CI had one in the first frames): what the run
  // set with Set gravity has to outlive it.
  await evaluate(`__gm.state.preview()`);
  await evaluate(`(() => {
    const out = (window.__physicsGraph = []);
    const start = performance.now();
    const sample = () => {
      const w = __gm.world();
      if (!w) return;
      const at = (id) => w.entities.find((e) => e.objectId === id);
      const kicked = at('phys-kicked');
      out.push({
        t: (performance.now() - start) / 1000,
        kickedX: kicked?.worldX,
        kickedY: kicked?.worldY,
        walker: at('phys-walker')?.worldX,
        pushed: at('phys-pushed')?.worldX,
      });
      if (performance.now() - start < 2000) requestAnimationFrame(sample);
    };
    requestAnimationFrame(sample);
  })()`);
  await sleep(2300);
  const run = await json('window.__physicsGraph');
  await stop();

  const at = (seconds) =>
    run.reduce((best, s) => (Math.abs(s.t - seconds) < Math.abs(best.t - seconds) ? s : best));
  const [early, late] = [at(0.5), at(1.5)];
  const glide = (late.kickedX - early.kickedX) / (late.t - early.t);
  const speed = KICK / KICKED_MASS;
  check(
    `Set gravity and Apply impulse in On start: the crate glides straight at impulse ÷ mass (${speed} per second)`,
    run.length > 60 &&
      Math.abs(glide - speed) < speed * 0.05 &&
      run.every((s) => Math.abs(s.kickedY - Y) < 0.5),
    JSON.stringify({ frames: run.length, glide: Math.round(glide * 10) / 10, early, late }),
  );
  const gap = Math.min(...run.map((s) => s.pushed - 20 - (s.walker + 20)));
  const pushed = run.at(-1).pushed - 60;
  check(
    'Move with "Collide with solids" pushes the crate in its way and never gets into it',
    pushed > 100 && gap > -0.01,
    JSON.stringify({
      pushed: Math.round(pushed * 10) / 10,
      walked: Math.round(run.at(-1).walker * 10) / 10,
      gap,
    }),
  );
  const hints = consoleLog.filter((line) => line.includes('[physics]')).slice(hintsBefore);
  check('nothing in the step made the physics hint at a no-op', hints.length === 0, hints.join(' | '));

  const clearPhysics = () =>
    mutate(`
    const p = __gm.state.project;
    const scene = __gm.state.activeScene;
    scene.objects = scene.objects.filter((o) => !o.id.startsWith('phys-'));
    p.assets = p.assets.filter((a) => !a.id.startsWith('phys-'));
    __gm.state.select(null)`);
  await clearPhysics();

  // 41d. Move along the contact normal (#150): a ball walked straight right into the upper-left
  //      corner of a block, 12 below its centre, rolls up over it instead of hanging on the corner,
  //      and its graph logs the normal of the first contact from Move's hit / normal outputs.
  const edgeLog = consoleLog.length;
  await mutate(`
    const scene = __gm.state.activeScene;
    const assets = __gm.state.project.assets;
    ${MAKE_OBJECT}
    const asset = structuredClone(assets.find((a) => a.id === 'mover'));
    Object.assign(asset, { id: 'phys-roll', name: 'Physics roll', props: { enabled: true, runInEditor: false }, variables: [], graph: ${JSON.stringify(rollGraph)} });
    assets.push(asset);
    assets.push({ id: 'phys-col-ball', type: 'collider', name: 'phys-col-ball', props: { shape: 'circle', width: 40, height: 40, radius: ${BALL_R}, isTrigger: false } });
    assets.push({ id: 'phys-col-block', type: 'collider', name: 'phys-col-block', props: { shape: 'box', width: 100, height: 60, radius: 20, isTrigger: false } });
    const put = (id, assetId, parentId, x, y, name, overrides = {}) => {
      const o = make(id, assetId, parentId, y, name);
      o.position.x = x;
      o.overrides = overrides;
      scene.objects.push(o);
    };
    put('phys-ball', 'crate', '', 0, ${Y}, 'Rolling ball', { width: 40, height: 40 });
    put('phys-ball-col', 'phys-col-ball', 'phys-ball', 0, 0);
    put('phys-ball-roll', 'phys-roll', 'phys-ball', 0, 0, 'Roll');
    put('phys-block', 'crate', '', 150, ${Y + CORNER_DROP + 30}, 'Edge block', { width: 100, height: 60 });
    put('phys-block-col', 'phys-col-block', 'phys-block', 0, 0);
    __gm.state.select(null)`);
  await play();
  await sleep(2000);
  const ball = await json(
    `(() => { const e = __gm.world()?.entities.find((x) => x.objectId === 'phys-ball'); return e && { x: e.worldX, y: e.worldY }; })()`,
  );
  await stop();
  const top = Y + CORNER_DROP - BALL_R; // the ball's centre when it rolls along the block's top face
  check(
    'Move rolls a ball up over the edge it runs into, onto the top face',
    ball && ball.x > 150 && ball.y <= top + 0.01 && ball.y > top - 3,
    JSON.stringify({ ball, top }),
  );
  const lines = consoleLog.slice(edgeLog).filter((line) => line.startsWith('[behavior '));
  const logged = lines
    .filter((line) => line.startsWith('[behavior Roll]'))
    .map((line) => Number(line.split(']').pop()));
  const reach = Math.sqrt(BALL_R ** 2 - CORNER_DROP ** 2);
  check(
    "Move's hit and normal outputs: the first contact faces from the corner to the ball's centre",
    logged.length >= 2 &&
      Math.abs(logged[0] + reach / BALL_R) < 1e-6 &&
      Math.abs(logged[1] + CORNER_DROP / BALL_R) < 1e-6,
    JSON.stringify({
      logged: logged.slice(0, 4),
      expected: [-reach / BALL_R, -CORNER_DROP / BALL_R],
      lines: lines.slice(0, 4),
    }),
  );
  await clearPhysics();

  // 41e. Joints (#154): a bob below a hook gets a joint from the hierarchy menu, is made a rope to
  //      the hook in the inspector, its far end is dragged by its handle in the scene view, and in
  //      the played scene the bob hangs where it would otherwise fall.
  await mutate(`
    const scene = __gm.state.activeScene;
    const assets = __gm.state.project.assets;
    ${MAKE_OBJECT}
    assets.push({ id: 'phys-col-box', type: 'collider', name: 'phys-col-box', props: { shape: 'box', width: 40, height: 40, radius: 20, isTrigger: false } });
    assets.push({ id: 'phys-rb-free', type: 'rigidbody', name: 'phys-rb-free', props: { bodyType: 'dynamic', mass: 0 } });
    const put = (id, assetId, parentId, x, y, name, overrides = {}) => {
      const o = make(id, assetId, parentId, y, name);
      o.position.x = x;
      o.overrides = overrides;
      scene.objects.push(o);
    };
    put('phys-hook', 'crate', '', 0, ${Y}, 'Physics hook', { width: 20, height: 20 });
    put('phys-bob', 'crate', '', 0, ${Y + 100}, 'Physics bob', { width: 40, height: 40 });
    put('phys-bob-col', 'phys-col-box', 'phys-bob', 0, 0);
    put('phys-bob-rb', 'phys-rb-free', 'phys-bob', 0, 0);
    put('phys-loose', 'crate', '', 200, ${Y + 100}, 'Physics loose', { width: 40, height: 40 });
    put('phys-loose-col', 'phys-col-box', 'phys-loose', 0, 0);
    put('phys-loose-rb', 'phys-rb-free', 'phys-loose', 0, 0);
    __gm.state.select(null)`);
  await showTab('scene');
  await evaluate(`__gm.lookAt(0, ${Y + 50})`);
  await selectObject('phys-bob');
  const bobRow = await inView(t, '__gm.leftColumn().objects', `__gm.hierarchyRow('phys-bob')`);
  const countBefore = (await objects()).length;
  await click(bobRow.x, bobRow.y, 'right');
  await clickText('Add joint…');
  if (await has('Create new joint')) await clickText('Create new joint');
  await press('Escape');
  await settle();
  const jointSelection = (await state()).selection;
  const joint = jointSelection?.kind === 'object' ? await object(jointSelection.objectId) : null;
  const jointAsset = joint && (await asset(joint.assetId));
  check(
    'Add joint puts a hinge below the object and shows its rows',
    (await objects()).length === countBefore + 1 &&
      joint?.parentId === 'phys-bob' &&
      jointAsset?.type === 'joint' &&
      jointAsset?.props?.jointType === 'hinge' &&
      (await has('Connected object')) &&
      (await has('Limit angle')) &&
      !(await has('Stiffness')) &&
      (await evaluate(`__gm.layerOf('${joint?.id}')`)) === 'overlay',
    JSON.stringify({ joint, jointAsset }),
  );
  const pressAt = async (at, what) => {
    if (!at) throw new Error(`41e: ${what} is not on screen`);
    await click(at.x, at.y);
    await settle();
  };
  await pressAt(await inView(t, '__gm.inspectorRect()', "__gm.inspectorField('Type')"), 'the Type field');
  await pressAt(await json("__gm.locate('Rope', true)"), 'Rope in the menu');
  await pressAt(
    await inView(t, '__gm.inspectorRect()', "__gm.inspectorField('Connected object')"),
    'the Connected object field',
  );
  // The menu lists every object of the scene: found by typing, as in a scene that has many.
  await typeText('Physics hook');
  await settle();
  await pressAt(await json("__gm.locate('Physics hook', true)"), 'Physics hook in the menu');
  const jointObject = async () => object(joint.id);
  const links = async () => json('__gm.joints()');
  const roped = await links();
  const ropeLink = roped.links.find((l) => l.id === joint?.id);
  check(
    'a rope connected to the hook is drawn from the bob to it, with a handle on its far end',
    (await jointObject())?.overrides?.jointType === 'rope' &&
      (await jointObject())?.overrides?.connected?.$object === 'phys-hook' &&
      ropeLink?.connectedId === 'phys-hook' &&
      ropeLink.anchored === true &&
      Math.abs(ropeLink.from.x) < 0.01 &&
      Math.abs(ropeLink.from.y - (Y + 100)) < 0.01 &&
      Math.abs(ropeLink.to.x) < 0.01 &&
      Math.abs(ropeLink.to.y - Y) < 0.01 &&
      roped.handle?.objectId === joint?.id &&
      (await has('Connected anchor X')) &&
      (await has('Length (0 = as placed)')) &&
      !(await has('Limit angle')),
    JSON.stringify({ roped, overrides: (await jointObject())?.overrides }),
  );
  await shot('41-joint');
  // The scale of the view, read off the bob's 40 units.
  const bobRect = await json(`__gm.objectRect('phys-bob')`);
  const unit = bobRect.w / 40;
  await drag(roped.handle.x, roped.handle.y, roped.handle.x + 30 * unit, roped.handle.y);
  await settle();
  const moved = (await jointObject())?.overrides;
  const movedLink = (await links()).links.find((l) => l.id === joint?.id);
  await undo();
  await settle();
  const undone = (await jointObject())?.overrides;
  check(
    "dragging the handle moves the rope's connected anchor, and one undo puts it back",
    Math.abs(moved?.connectedAnchorX - 30) <= 1 &&
      Math.abs(moved?.connectedAnchorY ?? 0) <= 1 &&
      Math.abs(movedLink?.to.x - moved?.connectedAnchorX) < 0.01 &&
      undone?.connectedAnchorX === undefined &&
      undone?.jointType === 'rope',
    JSON.stringify({ moved, movedLink, undone, unit }),
  );

  const jointHints = consoleLog.filter((line) => line.includes('[physics]')).length;
  await select(null);
  await play();
  await evaluate(`(() => {
    const out = (window.__jointSamples = []);
    const start = performance.now();
    const sample = () => {
      const w = __gm.world();
      if (!w) return;
      const y = (id) => w.entities.find((e) => e.objectId === id)?.worldY;
      out.push({ t: performance.now() - start, bob: y('phys-bob'), loose: y('phys-loose') });
      if (performance.now() - start < 1500) requestAnimationFrame(sample);
    };
    requestAnimationFrame(sample);
  })()`);
  await sleep(1800);
  const hung = await json('window.__jointSamples');
  await stop();
  const bobYs = hung.map((s) => s.bob);
  check(
    'in the played scene the bob hangs on its rope while the one without a joint falls',
    hung.length > 30 &&
      bobYs.every((y) => Math.abs(y - (Y + 100)) < 2) &&
      hung.at(-1).loose > Y + 400 &&
      consoleLog.filter((line) => line.includes('[physics]')).length === jointHints,
    JSON.stringify({
      frames: hung.length,
      bob: [Math.min(...bobYs), Math.max(...bobYs)],
      loose: hung.at(-1).loose,
      hints: consoleLog.filter((line) => line.includes('[physics]')).slice(jointHints),
    }),
  );
  await mutate(`
    const p = __gm.state.project;
    const scene = __gm.state.activeScene;
    const joints = new Set(scene.objects.filter((o) => o.parentId === 'phys-bob').map((o) => o.assetId));
    scene.objects = scene.objects.filter((o) => !o.id.startsWith('phys-') && o.parentId !== 'phys-bob');
    p.assets = p.assets.filter((a) => !a.id.startsWith('phys-') && !(a.type === 'joint' && joints.has(a.id)));
    __gm.state.select(null)`);
}