:root {
        --primary-color: #2041ff;
        --secondary-color: #6ea3ff;
        --accent-color: #ffffff;
        --light-color: #aff3ff;
        --text-color: #000000;
        --white: #ffffff;
        --success-color: #4caf50;
      }

      body {
        font-family: "Poppins", sans-serif;
        background: linear-gradient(
          135deg,
          hsl(215, 100%, 86%),
          #76b6ff,
          #5a7ca8
        );
        padding: 0;
        padding-top: 80px;
        min-height: 100vh;
        color: var(--text-color);
        background-size: 400% 400%;
        animation: gradientBG 15s ease infinite;
        text-align: center;
      }

      /* Header styles (sin cambios) */
      .header {
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        background: linear-gradient(
          135deg,
          var(--primary-color),
          var(--secondary-color)
        );
        padding: 0 10%;
        display: flex;
        align-items: center;
        justify-content: space-between;
        z-index: 1000;
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
        border-bottom: 2px solid #fff;
        transition: all 0.3s ease;
      }

      .logo {
        font-size: 25px;
        text-transform: uppercase;
        color: #ffffff;
        font-weight: 700;
      }

      .navigation ul {
        list-style: none;
        margin: 0;
        padding: 0;
      }

      .header .navigation ul li {
        float: left;
        position: relative;
      }

      .header .navigation ul li a {
        font-family: "Poppins", sans-serif;
        font-size: 16px;
        font-weight: 500;
        color: var(--white);
        text-decoration: none;
        padding: 22px 20px;
        display: block;
        transition: all 0.3s ease;
      }

      .header .navigation ul li a:hover {
        background-color: rgba(255, 255, 255, 0.733);
        transform: translateY(-2px);
        color: var(--primary-color);
      }

      .header .navigation ul li ul {
        position: absolute;
        right: 0;
        width: 220px;
        background: rgba(255, 255, 255, 0.95);
        border-radius: 0 0 8px 8px;
        box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
        display: none;
        overflow: hidden;
      }

      .header .navigation ul li ul li a {
        color: var(--text-color);
        padding: 12px 20px;
        font-size: 14px;
      }
      .header .navigation ul li ul li a:hover {
        background-color: var(--light-color);
        color: var(--primary-color);
      }

      .header .navigation ul li:hover > ul {
        display: initial;
        animation: fadeIn 0.3s ease-out;
      }

      #toggle,
      .header label {
        display: none;
        cursor: pointer;
      }

      .menu {
        width: 35px;
        height: 30px;
        filter: invert(1);
      }

      /* Main content */
      .container {
        max-width: 1200px;
        margin: 0 auto;
        padding: 20px;
      }

      h1 {
        color: #ffffff;
        margin-bottom: 20px;
        font-family: "Montserrat", sans-serif;
        font-size: 2.5rem;
        text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
      }

      /* Game styles */
      .game-container {
        background-color: rgba(255, 255, 255, 0.9);
        border-radius: 15px;
        padding: 30px;
        box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
        margin-bottom: 30px;
      }

      .memory-game {
        display: grid;
        grid-template-columns: repeat(6, 1fr);
        gap: 15px;
        margin: 0 auto;
        max-width: 900px;
      }

      .memory-card {
        height: 150px;
        background-color: #81d4fa;
        border-radius: 10px;
        cursor: pointer;
        display: flex;
        justify-content: center;
        align-items: center;
        transform-style: preserve-3d;
        transition: transform 0.5s;
        position: relative;
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
      }

      .memory-card:hover {
        transform: scale(1.02);
        box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
      }

      .memory-card.flip {
        transform: rotateY(180deg);
      }

      .front-face,
      .back-face {
        position: absolute;
        width: 100%;
        height: 100%;
        backface-visibility: hidden;
        display: flex;
        justify-content: center;
        align-items: center;
        border-radius: 10px;
      }

      .front-face {
        background-color: white;
        transform: rotateY(180deg);
        padding: 15px;
        box-sizing: border-box;
      }

      .img-card .front-face {
        padding: 10px;
      }

      .front-face img {
        max-width: 100%;
        max-height: 100%;
        object-fit: contain;
        border-radius: 5px;
      }

      .back-face {
        background-color: #6ea3ff;
        background-image: url("placeholder-beach-icon.jpg");
        background-size: 60px;
        background-repeat: no-repeat;
        background-position: center;
      }

      .text-card .front-face {
        font-size: 18px;
        font-weight: bold;
        text-align: center;
        color: #015d9b;
        padding: 10px;
      }

      /* Game info */
      .game-info {
        background-color: rgba(255, 255, 255, 0.8);
        border-radius: 10px;
        padding: 15px;
        margin-bottom: 20px;
        display: flex;
        justify-content: space-around;
        max-width: 500px;
        margin-left: auto;
        margin-right: auto;
      }

      .counter {
        font-size: 18px;
        font-weight: bold;
        color: #2c3e50;
      }

      .counter span {
        color: var(--primary-color);
        font-size: 20px;
      }

      /* Button styles */
      .controls {
        margin: 30px 0;
      }

      button {
        background-color: var(--primary-color);
        color: white;
        border: none;
        padding: 12px 25px;
        border-radius: 8px;
        cursor: pointer;
        font-size: 16px;
        font-weight: 600;
        transition: all 0.3s ease;
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
        display: inline-flex;
        align-items: center;
        gap: 10px;
      }

      button:hover {
        background-color: #0d3ef7;
        transform: translateY(-2px);
        box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
      }

      /* Congratulations modal */
      .congrats-modal {
        display: none;
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background-color: rgba(0, 0, 0, 0.8);
        z-index: 2000;
        align-items: center;
        justify-content: center;
        animation: fadeIn 0.3s ease-out;
      }

      .congrats-content {
        background: linear-gradient(135deg, #ffffff, #f8f9fa);
        padding: 40px;
        border-radius: 20px;
        text-align: center;
        max-width: 500px;
        width: 90%;
        box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
        position: relative;
        animation: slideUp 0.5s ease-out;
      }

      .congrats-content h2 {
        color: var(--primary-color);
        font-size: 2.2rem;
        margin-bottom: 20px;
        font-family: "Montserrat", sans-serif;
      }

      .congrats-content p {
        font-size: 1.1rem;
        margin-bottom: 30px;
        color: #495057;
      }

      .congrats-icon {
        font-size: 4rem;
        color: var(--success-color);
        margin-bottom: 20px;
        animation: bounce 1s infinite alternate;
      }

      .close-modal {
        background-color: var(--primary-color);
        color: white;
        border: none;
        padding: 12px 25px;
        border-radius: 8px;
        font-size: 1rem;
        cursor: pointer;
        transition: all 0.3s ease;
        font-weight: 600;
      }

      .close-modal:hover {
        background-color: #0d3ef7;
        transform: translateY(-2px);
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
      }

      /* Animations */
      @keyframes gradientBG {
        0% {
          background-position: 0% 50%;
        }
        50% {
          background-position: 100% 50%;
        }
        100% {
          background-position: 0% 50%;
        }
      }

      @keyframes fadeIn {
        from {
          opacity: 0;
        }
        to {
          opacity: 1;
        }
      }

      @keyframes slideUp {
        from {
          opacity: 0;
          transform: translateY(20px);
        }
        to {
          opacity: 1;
          transform: translateY(0);
        }
      }

      @keyframes bounce {
        from {
          transform: translateY(0);
        }
        to {
          transform: translateY(-10px);
        }
      }

      /* Responsive adjustments */
      @media (max-width: 950px) {
        .header label {
          display: initial;
        }
        .header {
          padding: 15px 5%;
        }
        .header .navigation {
          position: absolute;
          top: 100%;
          left: 0;
          right: 0;
          background-color: rgba(96, 107, 255, 0.95);
          display: none;
        }
        .header .navigation ul li {
          width: 100%;
        }
        .header .navigation ul li a {
          padding: 12px 5%;
        }
        .header .navigation ul li ul {
          position: relative;
          width: 100%;
          left: 0;
        }
        .header .navigation ul li ul li {
          background-color: rgba(116, 85, 255, 0.9);
        }
        #toggle:checked ~ .navigation {
          display: block;
        }

        .memory-game {
          grid-template-columns: repeat(4, 1fr);
        }
      }

      @media (max-width: 768px) {
        h1 {
          font-size: 2rem;
        }

        .memory-game {
          grid-template-columns: repeat(3, 1fr);
          gap: 10px;
        }

        .memory-card {
          height: 120px;
        }

        .text-card .front-face {
          font-size: 16px;
        }
      }

      @media (max-width: 480px) {
        .memory-game {
          grid-template-columns: repeat(2, 1fr);
        }

        .memory-card {
          height: 100px;
        }
      }