body {
        font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
        margin: 0;
        padding: 20px;
        background-color: #9acee2;
        color: #333;
      }
      .header {
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        background-color: rgba(1, 1, 1, 0.7);
        padding: 0px 10%;
        display: flex;
        align-items: center;
        justify-content: space-between;
        z-index: 1000;
      }
      .logo {
        font-size: 25px;
        text-transform: uppercase;
        color: #ffffff;
        font-weight: 700;
      }
      .navigation ul {
        list-style: none;
      }
      .header .navigation ul li {
        float: left;
        position: relative;
      }
      .header .navigation ul li a {
        font-size: 18px;
        color: #ffffff;
        text-decoration: none;
        padding: 20px;
        display: block;
        transition: all 0.2s ease;
      }
      .header .navigation ul li a:hover {
        background-color: #fe615c;
      }
      .header .navigation ul li ul {
        position: absolute;
        right: 0;
        width: 300px;
        background-color: rgba(1, 1, 1, 0.7);
        display: none;
      }

      .header .navigation ul li ul li a {
        font-size: 15px;
        text-transform: capitalize;
      }
      .header .navigation ul li ul li ul {
        position: absolute;
        top: 0;
        right: 300px;
      }
      .header .navigation ul li ul li {
        width: 100%;
      }
      .header .navigation ul li:hover > ul {
        display: initial;
      }
      #toggle,
      .header label {
        display: none;
        cursor: pointer;
      }
      .menu {
        width: 45px;
        height: 35px;
      }
      @media (max-width: 950px) {
        .header label {
          display: initial;
        }
        .header {
          padding: 20px 10%;
        }
        .header .navigation {
          position: absolute;
          top: 100%;
          left: 0;
          right: 0;
          background-color: rgba(1, 1, 1, 0.7);
          display: none;
        }
        .header .navigation ul li {
          width: 100%;
        }
        .header .navigation ul li a {
          padding: 8px 30px 8px 10%;
        }
        .header .navigation ul li ul {
          position: relative;
          width: 100%;
          left: 0;
        }
        .header .navigation ul li ul li {
          background-color: rgba(197, 193, 193, 0.7);
        }
        .header .navigation ul li ul li ul {
          position: relative;
          width: 100%;
          left: 0;
        }
        #toggle:checked ~ .navigation {
          display: block;
        }
      }

      h1 {
        text-align: center;
        color: #ffffff;
        margin-bottom: 30px;
        font-size: 2.2rem;
        padding-top: 60px;
      }

      .container {
        max-width: 800px;
        margin: 0 auto;
        background: white;
        border-radius: 10px;
        padding: 25px;
        box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15);
      }
      table {
        width: 100%;
        border-collapse: collapse;
        margin-bottom: 20px;
        border-radius: 5px;
        overflow: hidden;
      }
      th {
        background-color: #3498db;
        color: white;
        padding: 14px;
        text-align: left;
        font-weight: bold;
        font-size: 1.1rem;
      }
      td {
        padding: 14px;
        border-bottom: 1px solid #ddd;
        font-size: 1rem;
      }
      tr:hover {
        background-color: #f9f9f9;
      }
      .drop-zone {
        min-height: 50px;
        border: 2px dashed #bbb;
        border-radius: 5px;
        padding: 8px;
        text-align: center;
        color: #777;
        transition: all 0.3s ease;
        display: flex;
        align-items: center;
        justify-content: center;
      }
      .drop-zone:hover {
        border-color: #3498db;
        background-color: #f0f8ff;
      }
      .english-verb {
        background-color: #3498db;
        color: white;
        padding: 10px 14px;
        margin: 6px;
        border-radius: 5px;
        cursor: move;
        display: inline-block;
        user-select: none;
        transition: all 0.2s ease;
        box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
        font-weight: 500;
      }
      .english-verb:hover {
        transform: translateY(-2px);
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
      }
      .english-verbs-container {
        display: flex;
        flex-wrap: wrap;
        min-height: 110px;
        border: 2px dashed #bbb;
        border-radius: 8px;
        padding: 12px;
        margin-bottom: 25px;
        background-color: #f9f9f9;
      }
      .correct {
        background-color: #2ecc71;
        animation: pulse 0.5s;
      }
      .incorrect {
        background-color: #e74c3c;
        animation: shake 0.5s;
      }
      @keyframes pulse {
        0% {
          transform: scale(1);
        }
        50% {
          transform: scale(1.1);
        }
        100% {
          transform: scale(1);
        }
      }
      @keyframes shake {
        0%,
        100% {
          transform: translateX(0);
        }
        20%,
        60% {
          transform: translateX(-5px);
        }
        40%,
        80% {
          transform: translateX(5px);
        }
      }
      .button {
        display: inline-block;
        padding: 12px 20px;
        margin: 10px 5px;
        background-color: #3498db;
        color: white;
        border: none;
        border-radius: 5px;
        cursor: pointer;
        font-size: 16px;
        transition: all 0.3s ease;
        box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
        text-align: center;
      }
      .button:hover {
        background-color: #2980b9;
        transform: translateY(-2px);
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
      }
      .reset-btn {
        background-color: #e67e22;
      }
      .reset-btn:hover {
        background-color: #d35400;
      }
      .hint-btn {
        background-color: #9b59b6;
      }
      .hint-btn:hover {
        background-color: #8e44ad;
      }
      .check-btn {
        background-color: #2ecc71;
      }
      .check-btn:hover {
        background-color: #27ae60;
      }
      .buttons-container {
        display: flex;
        justify-content: center;
        margin-top: 20px;
        flex-wrap: wrap;
      }
      .score-container {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-bottom: 25px;
        padding: 15px;
        background-color: #ecf0f1;
        border-radius: 8px;
      }
      .score {
        font-size: 18px;
        color: #2c3e50;
        font-weight: bold;
      }
      .timer {
        font-size: 18px;
        color: #2c3e50;
        font-weight: bold;
      }
      .difficulty-selector {
        margin-bottom: 20px;
        text-align: center;
      }
      .difficulty-selector label {
        margin-right: 15px;
        font-weight: bold;
      }
      .difficulty-selector select {
        padding: 8px 15px;
        border-radius: 5px;
        border: 1px solid #ddd;
        font-size: 16px;
      }
      .level-info {
        margin-bottom: 20px;
        padding: 10px;
        background-color: #e8f4fc;
        border-radius: 5px;
        border-left: 4px solid #3498db;
        font-style: italic;
      }
      .progress-bar {
        height: 10px;
        background-color: #ecf0f1;
        border-radius: 5px;
        margin-top: 10px;
        overflow: hidden;
      }
      .progress {
        height: 100%;
        background-color: #3498db;
        width: 0%;
        transition: width 0.3s ease;
      }
      .completed-message {
        display: none;
        text-align: center;
        padding: 20px;
        background-color: #d5f5e3;
        border-radius: 8px;
        margin: 20px 0;
        font-weight: bold;
        color: #27ae60;
        font-size: 18px;
        animation: fadeIn 1s;
      }
      @keyframes fadeIn {
        from {
          opacity: 0;
        }
        to {
          opacity: 1;
        }
      }
      .english-header,
      .spanish-header {
        font-weight: bold;
        font-size: 18px;
        margin-bottom: 10px;
        color: #2c3e50;
      }
      .tooltip {
        position: relative;
        display: inline-block;
        margin-left: 10px;
        cursor: pointer;
      }
      .tooltip .tooltiptext {
        visibility: hidden;
        width: 200px;
        background-color: #555;
        color: #fff;
        text-align: center;
        border-radius: 6px;
        padding: 10px;
        position: absolute;
        z-index: 1;
        bottom: 125%;
        left: 50%;
        transform: translateX(-50%);
        opacity: 0;
        transition: opacity 0.3s;
      }
      .tooltip:hover .tooltiptext {
        visibility: visible;
        opacity: 1;
      }
      /* Responsive styles */
      @media (max-width: 600px) {
        .score-container {
          flex-direction: column;
          gap: 10px;
        }
        .buttons-container {
          flex-direction: column;
          gap: 10px;
        }
        .button {
          width: 100%;
          margin: 5px 0;
        }
      }