/* ============================================================
   《电磁场实验室》样式表
   纯 CSS，零外部依赖（无外部字体 / 图片 / CDN）
   ============================================================ */

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  height: 100%;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", "Microsoft YaHei", sans-serif;
  color: #e6e9ff;
  background: radial-gradient(circle at 50% 30%, #171a3a, #0b0e20);
  background-attachment: fixed;
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
}

/* ---------------- 玻璃拟态面板 ---------------- */
.glass {
  background: rgba(255, 255, 255, .06);
  border: 1px solid rgba(255, 255, 255, .12);
  border-radius: 20px;
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}

/* ---------------- 顶部栏 ---------------- */
.topbar {
  height: 56px;
  padding: 0 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid rgba(255, 255, 255, .08);
  background: rgba(10, 12, 30, .55);
}

.logo {
  font-size: 19px;
  font-weight: 700;
  letter-spacing: 2px;
  background: linear-gradient(90deg, #7c5cff, #22d3ee);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.btn-back {
  font-size: 13px;
  color: #c7cbff;
  text-decoration: none;
  padding: 8px 14px;
  border: 1px solid rgba(255, 255, 255, .18);
  border-radius: 999px;
  transition: all .18s ease;
  white-space: nowrap;
}
.btn-back:hover { border-color: #7c5cff; color: #fff; background: rgba(124, 92, 255, .18); }

/* ---------------- 标签栏 ---------------- */
.tabbar {
  display: flex;
  gap: 8px;
  padding: 10px 14px 0;
  overflow-x: auto;
  scrollbar-width: none;
}
.tabbar::-webkit-scrollbar { display: none; }

.tab-btn {
  flex: 0 0 auto;
  font: inherit;
  font-size: 13.5px;
  color: #b3b9e8;
  background: rgba(255, 255, 255, .04);
  border: 1px solid rgba(255, 255, 255, .10);
  border-bottom: none;
  border-radius: 14px 14px 0 0;
  padding: 9px 16px;
  cursor: pointer;
  transition: all .15s ease;
  white-space: nowrap;
}
.tab-btn:hover { color: #fff; background: rgba(124, 92, 255, .18); }
.tab-btn.active {
  color: #fff;
  background: rgba(124, 92, 255, .28);
  border-color: rgba(124, 92, 255, .75);
  box-shadow: inset 0 -2px 0 #22d3ee;
}

/* ---------------- 主区域布局 ---------------- */
.stage {
  position: absolute;
  left: 0; right: 0; top: 56px; bottom: 0;
  display: flex;
  flex-direction: column;
  padding: 0 14px 12px;
  gap: 10px;
}

/* ---------------- 公式条 ---------------- */
.formula-bar {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 6px 18px;
  padding: 8px 16px;
  margin-top: -1px;
}
.formula {
  font-size: 14px;
  font-weight: 600;
  color: #22d3ee;
  letter-spacing: .3px;
  white-space: nowrap;
}
.hint {
  font-size: 12px;
  color: #9aa0d4;
  line-height: 1.5;
}

/* ---------------- 工具栏 ---------------- */
.tool-panel {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding: 10px 14px;
}

.tool-page {
  display: none;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  flex: 1 1 auto;
  min-width: 0;
}
.tool-page.active { display: flex; }

.common-ctl {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
  padding-left: 12px;
  border-left: 1px solid rgba(255, 255, 255, .12);
}

.tool-label {
  font-size: 12px;
  color: #8d93c8;
  white-space: nowrap;
}

/* 分段选择器 */
.seg {
  display: inline-flex;
  border: 1px solid rgba(255, 255, 255, .14);
  border-radius: 10px;
  overflow: hidden;
}
.seg-btn {
  font: inherit;
  font-size: 12.5px;
  color: #c0c5f2;
  background: transparent;
  border: none;
  padding: 7px 11px;
  cursor: pointer;
  white-space: nowrap;
  transition: all .14s ease;
}
.seg-btn + .seg-btn { border-left: 1px solid rgba(255, 255, 255, .10); }
.seg-btn:hover { background: rgba(124, 92, 255, .18); color: #fff; }
.seg-btn.active {
  background: linear-gradient(135deg, rgba(124, 92, 255, .85), rgba(90, 70, 220, .85));
  color: #fff;
}
.seg-small .seg-btn { padding: 6px 12px; }

/* 普通按钮 */
.btn {
  font: inherit;
  font-size: 12.5px;
  color: #dfe3ff;
  background: rgba(255, 255, 255, .06);
  border: 1px solid rgba(255, 255, 255, .18);
  border-radius: 10px;
  padding: 7px 12px;
  cursor: pointer;
  white-space: nowrap;
  transition: all .14s ease;
}
.btn:hover { border-color: #7c5cff; background: rgba(124, 92, 255, .2); color: #fff; }
.btn:active { transform: translateY(1px); }
.btn-warn { color: #ffc9dd; }
.btn-warn:hover { border-color: #ff5ca8; background: rgba(255, 92, 168, .18); }
.toggle-on {
  border-color: rgba(34, 211, 238, .7);
  color: #a5f3fc;
  background: rgba(34, 211, 238, .12);
}
.toggle-off {
  border-color: rgba(255, 255, 255, .18);
  color: #8d93c8;
  background: rgba(255, 255, 255, .04);
}
.btn.is-paused {
  border-color: #ffb347;
  color: #ffe3b3;
  background: rgba(255, 179, 71, .15);
}

/* 滑块 */
.slider-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 12.5px;
  color: #b9bff0;
  white-space: nowrap;
}
.slider-label b { color: #22d3ee; font-weight: 600; min-width: 30px; text-align: right; }
.slider {
  -webkit-appearance: none;
  appearance: none;
  width: 110px;
  height: 4px;
  border-radius: 4px;
  background: linear-gradient(90deg, #7c5cff, #22d3ee);
  outline: none;
  cursor: pointer;
}
.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px; height: 16px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid #7c5cff;
  cursor: pointer;
}
.slider::-moz-range-thumb {
  width: 12px; height: 12px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid #7c5cff;
  cursor: pointer;
}

/* ---------------- 画布 ---------------- */
.canvas-wrap {
  position: relative;
  flex: 1 1 auto;
  min-height: 240px;
  overflow: hidden;
}
#cv {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
  touch-action: none;
  cursor: crosshair;
}

/* 读数浮层 */
.readout {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: calc(100% - 24px);
  font-size: 12px;
  line-height: 1.7;
  color: #cfd4ff;
  background: rgba(8, 10, 26, .66);
  border: 1px solid rgba(255, 255, 255, .12);
  border-radius: 12px;
  padding: 8px 12px;
  pointer-events: none;
  white-space: pre-line;
  text-align: left;
}
.readout .rd-title { color: #ffb347; font-weight: 700; margin-right: 6px; }
.readout .rd-ok { color: #22d3ee; font-weight: 700; }
.readout .rd-bad { color: #ff5ca8; font-weight: 700; }
.readout .rd-eq { color: #c4b5fd; }

/* ---------------- 响应式：手机端 ---------------- */
@media (max-width: 720px) {
  .topbar { height: 50px; padding: 0 12px; }
  .logo { font-size: 16px; letter-spacing: 1px; }
  .btn-back { padding: 6px 10px; font-size: 12px; }
  .stage { top: 50px; padding: 0 8px 8px; gap: 8px; }
  .tab-btn { font-size: 12.5px; padding: 8px 12px; }
  .formula-bar { padding: 7px 12px; gap: 2px 12px; }
  .formula { font-size: 12.5px; }
  .hint { font-size: 11px; }
  .tool-panel { padding: 8px 10px; gap: 6px; }
  .common-ctl {
    flex-basis: 100%;
    padding-left: 0;
    border-left: none;
    border-top: 1px solid rgba(255, 255, 255, .10);
    padding-top: 6px;
  }
  .seg-btn { padding: 8px 10px; font-size: 12px; }
  .btn { padding: 8px 10px; }
  .slider { width: 90px; }
  .readout { font-size: 11px; line-height: 1.55; padding: 6px 10px; }
}