.headphone-tool {
      width: 100%;
      max-width: 800px;
      height: 700px;
      margin: 0 auto;
      background: #ffffff;
      border: 1px solid #e5e7eb;
      border-radius: 18px;
      box-shadow: 0 10px 35px rgba(20, 25, 40, 0.10);
      overflow: hidden;
      display: flex;
      flex-direction: column;
    }

    .tool-header {
      padding: 17px 22px;
      background: linear-gradient(135deg, #171717, #343434);
      color: #ffffff;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
    }

    .tool-header h2 {
      font-size: 21px;
      font-weight: 700;
      margin: 0;
    }

    .tool-header p {
      font-size: 12px;
      color: #d0d0d0;
      margin: 5px 0 0;
    }

    .header-icon {
      width: 44px;
      height: 44px;
      display: flex;
      justify-content: center;
      align-items: center;
      border-radius: 12px;
      background: rgba(255,255,255,0.12);
      font-size: 25px;
      flex-shrink: 0;
    }

    .tool-body {
      padding: 17px;
      display: grid;
      grid-template-columns: 1.05fr 0.95fr;
      gap: 15px;
      flex: 1;
      min-height: 0;
    }

    .tool-panel {
      background: #fafbfc;
      border: 1px solid #e8ebef;
      border-radius: 13px;
      padding: 15px;
      min-width: 0;
      box-shadow: 0 3px 10px rgba(0,0,0,0.035);
    }

    .panel-title {
      font-size: 14px;
      font-weight: 700;
      margin-bottom: 12px;
      color: #202531;
    }

    .stereo-display {
      min-height: 120px;
      border-radius: 12px;
      padding: 14px 10px;
      background: linear-gradient(145deg, #161616, #303030);
      color: white;
      display: flex;
      justify-content: space-around;
      align-items: center;
      position: relative;
      overflow: hidden;
      margin-bottom: 13px;
    }

    .channel {
      text-align: center;
      width: 45%;
    }

    .ear-icon {
      font-size: 32px;
      opacity: 0.65;
      transition: 0.2s;
    }

    .channel.active .ear-icon {
      opacity: 1;
      filter: drop-shadow(0 0 8px #ffffff);
    }

    .channel-label {
      font-size: 12px;
      font-weight: 700;
      margin-top: 5px;
    }

    .channel-status {
      font-size: 10px;
      color: #b9b9b9;
      margin-top: 3px;
    }

    .channel.active .channel-status {
      color: #ffffff;
    }

    .sound-card {
      background: #ffffff;
      border: 1px solid #e5e7eb;
      border-radius: 10px;
      padding: 10px;
      margin-bottom: 8px;
    }

    .sound-card h6 {
      font-size: 12px;
      font-weight: 700;
      margin: 0 0 3px;
    }

    .sound-card p {
      color: #777f8c;
      font-size: 10px;
      margin: 0;
      line-height: 1.5;
    }

    .test-btn {
      width: 100%;
      border: 1px solid #484848;
      background: linear-gradient(135deg, #090909, #3b3b3b);
      color: #ffffff;
      border-radius: 8px;
      padding: 8px 9px;
      font-size: 12px;
      font-weight: 600;
      transition: transform 0.2s, box-shadow 0.2s;
    }
    .tests-btn{
      width: 50%;
      border: 1px solid #484848;
      background: linear-gradient(135deg, #090909, #3b3b3b);
      color: #ffffff;
      border-radius: 8px;
      padding: 8px 9px;
      font-size: 12px;
      font-weight: 600;
      transition: transform 0.2s, box-shadow 0.2s;
    }

    .test-btn:hover {
      color: #ffffff;
      background: linear-gradient(135deg, #303030, #050505);
      transform: translateY(-1px);
      box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    }

    .test-btn:focus-visible,
    .control-btn:focus-visible {
      outline: 3px solid #8bbcff;
      outline-offset: 2px;
    }

    .test-btn:disabled,
    .control-btn:disabled {
      opacity: 0.45;
      cursor: not-allowed;
      transform: none;
    }

    .control-btn {
      border: 1px solid #252525;
      background: linear-gradient(135deg, #090909, #383838);
      color: #ffffff;
      border-radius: 8px;
      padding: 9px 12px;
      font-size: 12px;
      font-weight: 600;
    }

    .control-btn:hover {
      color: #ffffff;
      background: linear-gradient(135deg, #303030, #080808);
    }

    .control-btn:disabled {
      opacity: 0.45;
    }

    .volume-value {
      font-size: 12px;
      font-weight: 700;
      color: #30343b;
    }

    .form-range {
      accent-color: #222222;
    }

    .setting-label {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      font-size: 12px;
      font-weight: 600;
      margin-bottom: 5px;
    }

    .status-box {
      background: #ffffff;
      border: 1px solid #e5e7eb;
      border-radius: 9px;
      padding: 10px;
      margin-top: 12px;
    }

    .status-indicator {
      width: 8px;
      height: 8px;
      background: #a1a1aa;
      border-radius: 50%;
      display: inline-block;
      margin-right: 6px;
    }

    .status-indicator.playing {
      background: #22a06b;
      box-shadow: 0 0 0 3px rgba(34,160,107,0.12);
    }

    #statusText {
      font-size: 11px;
      font-weight: 700;
    }

    #statusDetail {
      font-size: 10px;
      color: #737b88;
      margin-top: 5px;
      line-height: 1.5;
    }

    .balance-ends {
      display: flex;
      justify-content: space-between;
      font-size: 10px;
      color: #777f8c;
    }

    .frequency-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 7px;
      margin-top: 8px;
    }

    .frequency-grid .test-btn {
      padding: 9px 3px;
      font-size: 11px;
    }

    .tool-footer {
      padding: 9px 17px;
      border-top: 1px solid #eceef2;
      background: #ffffff;
      color: #747b87;
      font-size: 10px;
      display: flex;
      justify-content: space-between;
      gap: 10px;
    }

    @media (max-width: 600px) {
      body {
        padding: 10px 6px;
      }

      .headphone-tool {
        height: auto;
        min-height: 600px;
        overflow: visible;
      }

      .tool-header {
        padding: 15px;
      }

      .tool-header h2 {
        font-size: 18px;
      }

      .tool-body {
        grid-template-columns: 1fr;
        padding: 12px;
      }

      .tool-panel {
        padding: 13px;
      }

      .stereo-display {
        min-height: 105px;
      }

      .tool-footer {
        flex-wrap: wrap;
      }
    }

    @media (prefers-reduced-motion: reduce) {
      *, *::before, *::after {
        transition: none !important;
      }
    }