<!doctype html>
<meta charset="utf-8">
<title>25 pointer continuity</title>
<link rel="stylesheet" href="../_style.css">
<script src="../_lib.js"></script>
<body>
<main>
  <p>Goal: click <b>A</b>, then click <b>B</b>. Page requires pointer continuity:
     between the two clicks there must be intermediate <code>pointermove</code> events
     whose path roughly connects the two click points (no teleport). Two clicks
     &gt;100px apart with zero moves between is a synthetic-bridge tell.</p>
  <div style="display:flex;justify-content:space-between;margin-top:20px">
    <button id="a" style="padding:14px 22px;background:#36c;color:#fff;border:0;border-radius:6px">A</button>
    <div style="flex:1"></div>
    <button id="b" style="padding:14px 22px;background:#c36;color:#fff;border:0;border-radius:6px">B</button>
  </div>
</main>
<script>
Challenge.init({ id: "pointer-continuity", instructions: "click A, move mouse to B, click B" });

const a = document.getElementById("a");
const b = document.getElementById("b");

const moves = [];
window.addEventListener("pointermove", (e) => {
  moves.push({ x: e.clientX, y: e.clientY, t: e.timeStamp });
  if (moves.length > 500) moves.shift();
});

let aClickTs = 0, aPoint = null;
a.addEventListener("click", (e) => {
  if (!e.isTrusted) return Challenge.fail("A click isTrusted=false");
  aClickTs = e.timeStamp;
  aPoint = { x: e.clientX, y: e.clientY };
  Challenge.log("A click", aPoint);
});

b.addEventListener("click", (e) => {
  if (!aClickTs) return Challenge.fail("B clicked before A");
  if (!e.isTrusted) return Challenge.fail("B click isTrusted=false");
  const bPoint = { x: e.clientX, y: e.clientY };
  const between = moves.filter(m => m.t > aClickTs && m.t < e.timeStamp);
  Challenge.log("B click", { bPoint, betweenCount: between.length });
  const dist = Math.hypot(bPoint.x - aPoint.x, bPoint.y - aPoint.y);
  if (dist < 100) return Challenge.fail(`A-B distance only ${dist.toFixed(0)}px — buttons should be further apart in viewport`);
  if (between.length < 5) return Challenge.fail(`only ${between.length} pointermove(s) between A and B (need ≥5)`);

  // Path coverage: at least some intermediate move must be ≥30% of the way across.
  const inSpan = between.filter(m => {
    const px = (m.x - aPoint.x) / (bPoint.x - aPoint.x || 1);
    return px > 0.25 && px < 0.75;
  });
  if (inSpan.length === 0) return Challenge.fail("no pointermove samples in mid-span between A and B (teleport)");

  // Move timestamps should be spread, not bunched in <20ms.
  const span = between[between.length-1].t - between[0].t;
  if (span < 30) return Challenge.fail(`pointermoves bunched in ${span.toFixed(0)}ms (need spread ≥30ms)`);

  Challenge.pass(`${between.length} moves bridging A→B over ${span.toFixed(0)}ms, dist=${dist.toFixed(0)}px`);
});
</script>
</body>