body {
      font-family: Arial, sans-serif;
      background: #f4f4f4;
      margin: 0;
      padding: 20px;
      font-size: 18px;
      transition: background-color 0.3s ease, color 0.3s ease;
    }

    h1 {
      text-align: center;
      color: #333;
      margin-bottom: 30px;
      font-size: 28px;
    }

    .tabs {
      display: flex;
      justify-content: center;
      flex-wrap: wrap;
      margin-bottom: 20px;
    }

    .tab-button {
      background: #0077cc;
      color: white;
      border: none;
      padding: 12px 24px;
      margin: 6px;
      cursor: pointer;
      border-radius: 6px;
      font-size: 2em;
    }

    .tab-button.active {
      background: #005fa3;
    }

    .reset-buttons {
      text-align: center;
      margin: 20px 0;
    }

    .reset-buttons button,
    .reset-buttons label.button-like {
      background: #cc0000;
      color: white;
      border: none;
      padding: 10px 20px;
      margin: 5px;
      cursor: pointer;
      border-radius: 5px;
      font-size: 2em;
      display: inline-block;
    }

    .reset-buttons .secondary {
      background: #0077cc;
    }

    .dia {
      display: none;
      background: #fff;
      border-radius: 8px;
      padding: 20px;
      box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    }

    .dia.active {
      display: block;
    }

    .dia h2 {
      color: #0077cc;
      border-bottom: 2px solid #0077cc;
      padding-bottom: 5px;
      font-size: 24px;
    }

    .ejercicio {
      margin-top: 50px;
      padding: 15px;
      border-left: 4px solid #0077cc;
      background-color: #f9f9f9;
      border-radius: 5px;
      transition: all 0.3s ease;
    }

    .ejercicio.completado {
      opacity: 0.6;
      border-left: 4px solid #cc0000;
    }

    .ejercicio h3 {
      margin-top: 0;
      color: #444;
      font-size: 22px;
    }

    .ejercicio input[type="checkbox"] {
      transform: scale(1.2);
      margin-right: 10px;
    }

    .seccion {
      margin: 12px 0;
      font-size: 18px;
      line-height: 1.6;
    }

    .seccion strong {
      width: 160px;
      color: #222;
      font-weight: bold;
    }

    .video-container {
      position: relative;
      padding-bottom: 56.25%;
      height: 0;
      overflow: hidden;
      margin-top: 10px;
    }

    .video-container iframe {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      border: none;
    }

    @media (max-width: 600px) {
      body {
        font-size: 22px;
        padding: 15px;
      }

      h1 {
        font-size: 30px;
      }

      .tab-button {
        font-size: 24px;
        padding: 16px 28px;
        margin: 10px 6px;
        border-radius: 8px;
      }

      .dia h2 {
        font-size: 26px;
      }

      .ejercicio h3 {
        font-size: 24px;
      }

      .seccion {
        font-size: 22px;
        line-height: 1.7;
      }

      .seccion strong {
        font-size: 22px;
        display: block;
        margin-bottom: 6px;
        color: #000;
      }
    }

    /* Estilo base del checkbox */
    input[type="checkbox"] {
      appearance: none;
      -webkit-appearance: none;
      width: 40px;
      height: 40px;
      border: 2px solid #aaa;
      border-radius: 6px;
      background-color: #fff;
      position: relative;
      vertical-align: middle;
      margin-right: 10px;
      cursor: pointer;
      transition: all 0.3s ease;
    }

    /* Estilo cuando está marcado */
    input[type="checkbox"]:checked {
      background-color: #4CAF50;
      border-color: #4CAF50;
    }

    /* Icono de check */
    input[type="checkbox"]:checked::after {
      content: "✔";
      color: white;
      font-size: 30px;
      position: absolute;
      top: 1px;
      left: 4px;
    }

    /* Estilo del texto del label */
    label {
      font-size: 2em;
      font-weight: 500;
      cursor: pointer;
      display: flex;
      align-items: center;
      text-decoration: underline;
    }

    body.dark-mode {
      background-color: #121212;
      color: #e0e0e0;
    }

    .dark-mode .tab {
      background-color: #1e1e1e;
      border-color: #333;
      color: #e0e0e0;
    }

    .dark-mode .tab.active {
      background-color: #333;
    }

    .dark-mode .exercise {
      background-color: #1e1e1e;
      border-color: #444;
    }

    .dark-mode input[type="checkbox"] {
      accent-color: #00bcd4;
    }

    .dark-mode button {
      background-color: #333;
      color: #fff;
      border: 1px solid #555;
    }

    .dark-mode .ejercicio {
      background-color: #1e1e1e;
      border-color: #444;
    }

    .dark-mode .ejercicio {
      background-color: #1e1e1e;
      border-color: #444;
      color: #e0e0e0;
    }

    .dark-mode .ejercicio h3,
    .dark-mode .seccion strong {
      color: #e0e0e0;
    }

    #toggle-dark {
      font-size: 1.8em;
      background-color: #0077cc;
      color: white;
      border: none;
      padding: 10px 16px;
      border-radius: 8px;
      cursor: pointer;
      transition: background-color 0.3s ease, color 0.3s ease;
      float: right;
    }

    /* Estilo en modo oscuro */
    body.dark-mode #toggle-dark {
      background-color: #333;
      color: #fff;
      border: 1px solid #555;
    }

    #cuenta-atras {
      margin-top: 20px;
      font-family: sans-serif;
      display:flex;
      align-items:center;
      gap:10px;
      font-family:sans-serif;
      margin-top:20px;
      font-size: 2em;
      margin-bottom: 50px;
    }
    #cuenta-atras button, #cuenta-atras input, #cuenta-atras #tiempo{
      font-size: 1.8em;
    }

    #contador {
      font-size: 2em;
      margin: 10px 0;
    }

    video {
      width: 100%;
    }

    .fotos-container img {
      width: 100%;
    }

    .btn-descanso {
      display: contents;
    }