* {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: Arial, Helvetica, sans-serif;
      background: #f0f0f0;
      display: flex;
      flex-direction: column;
      min-height: 100vh;
    }

    /* Header */
    header {
      background-color: #ffffff;
      padding: 15px 30px;
      display: flex;
      justify-content: space-between;
      align-items: center;
      box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    }

    .logo {
      font-weight: bold;
      font-size: 1.2em;
      color: #333;
    }

    .menu {
      display: flex;
      gap: 20px;
    }

    .menu a {
      text-decoration: none;
      color: #007BFF;
      font-weight: bold;
      transition: color 0.3s ease;
    }

    .menu a:hover {
      color: #0056b3;
    }

    /* Main Section */
    main {
      flex: 1;
      display: flex;
      justify-content: center;
      align-items: flex-start;
      padding: 40px 20px;
    }

    .container {
      display: flex;
      gap: 50px;
      flex-wrap: wrap;
      justify-content: center;
    }

    .timer-box {
      background: #fff;
      padding: 30px;
      border-radius: 10px;
      box-shadow: 0 4px 20px rgba(0,0,0,0.1);
      width: 300px;
      text-align: center;
    }

    .time-display {
      font-size: 2em;
      margin: 20px 0;
      font-weight: bold;
    }

    button {
      padding: 10px 15px;
      margin: 5px;
      border: none;
      background: #007BFF;
      color: white;
      font-weight: bold;
      border-radius: 5px;
      cursor: pointer;
    }

    button:hover {
      background: #0056b3;
    }

    input[type="number"] {
      width: 60px;
      padding: 5px;
      margin: 0 5px;
    }
    
    /* Stopwatch Button Colors */
	.start-btn {
	    background: #28a745 !important; /* Green */
	    color: white;
	}
	
	.start-btn:hover {
	    background: #218838 !important;
	}
	
	.stop-btn {
	    background: #dc3545 !important; /* Red */
	    color: white;
	}
	
	.stop-btn:hover {
	    background: #c82333 !important;
	}
	
	.reset-btn {
	    background: #ffc107 !important; /* Yellow */
	    color: black;
	}
	
	.reset-btn:hover {
	    background: #e0a800 !important;
	}
    
    .about-container {
      max-width: 800px;
      margin: 0 auto;
      text-align: left;
      padding: 20px;
      background: #fff;
      border-radius: 10px;
      box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    }

    .about-container h1 {
      font-size: 2.5em;
      margin-bottom: 20px;
      color: #333;
    }

    .about-container h2 {
      font-size: 1.8em;
      margin-top: 30px;
      color: #333;
    }

    .about-container p {
      line-height: 1.6;
      font-size: 1.1em;
      color: #555;
    }
    
    .calculator {
        width: 340px;
        background: #C4C4C4;
        padding: 20px;
        border-radius: 12px;
        margin: auto;
        color: #222;
        box-shadow: 0 6px 15px rgba(0,0,0,0.1);
    }

    .display {
        width: 100%;
        height: 55px;
        font-size: 22px;
        text-align: right;
        padding: 10px;
        margin-bottom: 12px;
        border: 1px solid #ccc;
        border-radius: 6px;
        background: #ffffff;
        color: #000;
    }

    .buttons {
        display: grid;
        grid-template-columns: repeat(4, 1fr);
        gap: 8px;
        margin-bottom: 10px;
    }

    button {
        padding: 15px;
        font-size: 16px;
        border: 1px solid #ccc;
        border-radius: 6px;
        cursor: pointer;
        background: #ffffff;
        color: #000;
        transition: 0.2s;
    }

    button:hover {
        background: #f0f0f0;
    }

    /* Operators */
    .operator {
        background: #FFBF00;
    }

    /* Scientific buttons */
    .scientific {
        background: #d5d5d5;
    }

    /* Equal & Clear */
    .equal {
        background: #28a745;
        color: white;
    }

    .clear {
        background: #dc3545;
        color: white;
    }

    #scientificButtons {
        display: none;
    }

    .toggle-btn {
        margin-bottom: 10px;
        width: 100%;
        padding: 8px;
        background: #007bff;
        color: #000;
        border-radius: 6px;
        border: none;
        cursor: pointer;
    }

    h2 {
        text-align: center;
    }

    /* Footer */
    footer {
      background-color: #ffffff;
      padding: 15px;
      text-align: center;
      color: #777;
      border-top: 1px solid #ddd;
      font-size: 0.9em;
    }