* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

html, body {
  height: 100%;
  background: #000;
  color: #fff;
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Helvetica Neue", sans-serif;
  overflow: hidden;
}

.hidden { display: none !important; }

/* ---------- 启动屏 ---------- */
.start-screen {
  position: fixed;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 18px;
  text-align: center;
  padding: 24px;
  background: radial-gradient(circle at 50% 30%, #1a2a3a, #000);
}
.start-screen h1 { font-size: 28px; }
.start-screen p { color: #9fb3c8; font-size: 15px; }
.start-screen .hint { font-size: 12px; color: #5f7184; max-width: 280px; }

#startBtn {
  margin-top: 12px;
  padding: 16px 36px;
  font-size: 18px;
  font-weight: 600;
  color: #fff;
  background: #007aff;
  border: none;
  border-radius: 14px;
  cursor: pointer;
}
#startBtn:active { background: #0063cc; }

/* ---------- 舞台（视频 + 叠加层） ---------- */
.stage {
  position: fixed;
  inset: 0;
}
#video, .overlay {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}
#video { object-fit: cover; }       /* 视频铺满 */
.overlay { pointer-events: none; }  /* 叠加层不挡触摸 */

/* ---------- HUD ---------- */
.hud {
  position: absolute;
  top: env(safe-area-inset-top, 12px);
  left: 0;
  right: 0;
  padding: 16px 20px;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  pointer-events: none;
}
.hud-speed {
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(8px);
  border-radius: 14px;
  padding: 8px 16px;
  display: flex;
  align-items: baseline;
  gap: 6px;
}
.hud-speed #speedValue { font-size: 44px; font-weight: 700; line-height: 1; }
.hud-speed .unit { font-size: 14px; color: #9fb3c8; }

.hud-status {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 6px;
}
.status, .fps {
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(8px);
  border-radius: 10px;
  padding: 6px 10px;
  font-size: 12px;
}
.fps { color: #6ee7a0; }