<div class="lsw-wrap">
  <div class="lsw-display" id="lswDisplay">00:00.00</div>

  <div class="lsw-controls">
    <button class="lsw-btn lsw-btn-primary" id="lswStartBtn">Start</button>
    <button class="lsw-btn" id="lswLapBtn" disabled>Lap</button>
    <button class="lsw-btn" id="lswResetBtn">Reset</button>
  </div>

  <div class="lsw-laps" id="lswLaps"></div>
</div>

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: system-ui, -apple-system, sans-serif; background: #f8fafc; min-height: 100vh; display: flex; align-items: center; justify-content: center; padding: 24px; }

.lsw-wrap { width: 100%; max-width: 360px; background: #fff; border: 1px solid #e2e8f0; border-radius: 20px; padding: 26px; box-shadow: 0 16px 36px rgba(30,41,59,0.08); }

.lsw-display { text-align: center; font-size: 42px; font-weight: 800; color: #1e293b; font-variant-numeric: tabular-nums; letter-spacing: -1px; margin-bottom: 22px; }

.lsw-controls { display: flex; gap: 8px; margin-bottom: 18px; }
.lsw-btn {
  flex: 1; padding: 11px; border-radius: 11px; border: 1.5px solid #e2e8f0; background: #fff; color: #475569;
  font-size: 13px; font-weight: 700; font-family: inherit; cursor: pointer; transition: all 0.15s;
}
.lsw-btn:hover:not(:disabled) { background: #f8fafc; }
.lsw-btn:disabled { opacity: 0.45; cursor: not-allowed; }
.lsw-btn-primary { background: #6366f1; border-color: #6366f1; color: #fff; }
.lsw-btn-primary:hover:not(:disabled) { background: #4f46e5; }
.lsw-btn-primary.lsw-stop { background: #ef4444; border-color: #ef4444; }
.lsw-btn-primary.lsw-stop:hover { background: #dc2626; }

.lsw-laps { max-height: 200px; overflow-y: auto; }
.lsw-lap-row {
  display: flex; align-items: center; justify-content: space-between; padding: 9px 10px; border-radius: 8px;
  font-size: 12px; font-variant-numeric: tabular-nums;
}
.lsw-lap-row:nth-child(odd) { background: #f8fafc; }
.lsw-lap-num { font-weight: 800; color: #6366f1; width: 42px; flex-shrink: 0; }
.lsw-lap-split { color: #64748b; flex: 1; text-align: center; }
.lsw-lap-total { color: #1e293b; font-weight: 700; width: 80px; text-align: right; }
.lsw-laps-empty { text-align: center; color: #94a3b8; font-size: 12px; padding: 12px 0; }

const display = document.getElementById('lswDisplay');
const startBtn = document.getElementById('lswStartBtn');
const lapBtn = document.getElementById('lswLapBtn');
const resetBtn = document.getElementById('lswResetBtn');
const lapsEl = document.getElementById('lswLaps');

let running = false;
let startTimestamp = 0;
let accumulatedMs = 0;
let rafId = null;
let laps = [];

function formatTime(ms) {
  const totalMs = Math.max(0, ms);
  const minutes = Math.floor(totalMs / 60000);
  const seconds = Math.floor((totalMs % 60000) / 1000);
  const centis = Math.floor((totalMs % 1000) / 10);
  return String(minutes).padStart(2, '0') + ':' + String(seconds).padStart(2, '0') + '.' + String(centis).padStart(2, '0');
}

function currentElapsed() {
  if (running) return accumulatedMs + (Date.now() - startTimestamp);
  return accumulatedMs;
}

function renderDisplay() {
  display.textContent = formatTime(currentElapsed());
}

function loop() {
  renderDisplay();
  if (running) rafId = requestAnimationFrame(loop);
}

function renderLaps() {
  if (laps.length === 0) {
    lapsEl.innerHTML = '<div class="lsw-laps-empty">No laps recorded yet.</div>';
    return;
  }
  const rows = [];
  for (let i = laps.length - 1; i >= 0; i--) {
    const total = laps[i];
    const prevTotal = i > 0 ? laps[i - 1] : 0;
    const split = total - prevTotal;
    rows.push(`
      <div class="lsw-lap-row">
        <span class="lsw-lap-num">Lap ${i + 1}</span>
        <span class="lsw-lap-split">+${formatTime(split)}</span>
        <span class="lsw-lap-total">${formatTime(total)}</span>
      </div>`);
  }
  lapsEl.innerHTML = rows.join('');
}

startBtn.addEventListener('click', () => {
  if (running) {
    running = false;
    accumulatedMs += Date.now() - startTimestamp;
    cancelAnimationFrame(rafId);
    startBtn.textContent = 'Start';
    startBtn.classList.remove('lsw-stop');
    lapBtn.disabled = true;
    renderDisplay();
  } else {
    running = true;
    startTimestamp = Date.now();
    startBtn.textContent = 'Stop';
    startBtn.classList.add('lsw-stop');
    lapBtn.disabled = false;
    loop();
  }
});

lapBtn.addEventListener('click', () => {
  if (!running) return;
  laps.push(currentElapsed());
  renderLaps();
});

resetBtn.addEventListener('click', () => {
  running = false;
  cancelAnimationFrame(rafId);
  accumulatedMs = 0;
  laps = [];
  startBtn.textContent = 'Start';
  startBtn.classList.remove('lsw-stop');
  lapBtn.disabled = true;
  renderDisplay();
  renderLaps();
});

renderDisplay();
renderLaps();