* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    :root {
      --bg-primary: linear-gradient(135deg, #0f0f23 0%, #1a1a2e 50%, #16213e 100%);
      --bg-secondary: #0f0f23;
      --bg-card: rgba(45, 55, 72, 0.9);
      --text-primary: #e2e8f0;
      --text-secondary: #a0aec0;
      --accent: #81e6d9;
      --accent-hover: #68d391;
      --border: rgba(255, 255, 255, 0.1);
      --shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
      --glow: 0 0 20px rgba(129, 230, 217, 0.3);
    }

    body.dark {
      /* Dark mode styles removed since we're now permanently dark */
    }

    body {
      font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
      margin: 0;
      padding: 0;
      background: var(--bg-primary);
      color: var(--text-primary);
      min-height: 100vh;
      transition: all 0.3s ease;
      overflow-x: hidden;
      position: relative;
    }

    body::before {
      content: '';
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: radial-gradient(ellipse at top, rgba(129, 230, 217, 0.1) 0%, transparent 50%),
                  radial-gradient(ellipse at bottom right, rgba(104, 211, 145, 0.1) 0%, transparent 50%);
      pointer-events: none;
      z-index: -1;
    }

    .stars {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      pointer-events: none;
      z-index: 0;
    }

    .star {
      position: absolute;
      background: white;
      border-radius: 50%;
      opacity: 0.8;
      animation: twinkle 3s infinite ease-in-out;
    }

    .star:nth-child(odd) {
      animation-delay: 1s;
    }

    .star:nth-child(3n) {
      animation-delay: 2s;
    }

    .moon {
      position: fixed;
      top: 10%;
      right: 10%;
      width: 80px;
      height: 80px;
      background: linear-gradient(145deg, #ffd700, #ffed4e);
      border-radius: 50%;
      box-shadow: 0 0 30px rgba(255, 215, 0, 0.3),
                  inset -10px -10px 0 rgba(0, 0, 0, 0.1);
      animation: moonGlow 4s ease-in-out infinite alternate;
      z-index: 1;
    }

    .moon::before {
      content: '';
      position: absolute;
      top: 20%;
      left: 20%;
      width: 15px;
      height: 12px;
      background: rgba(0, 0, 0, 0.1);
      border-radius: 50%;
      box-shadow: 25px 5px 0 -2px rgba(0, 0, 0, 0.1),
                  10px 20px 0 -3px rgba(0, 0, 0, 0.1);
    }

    @keyframes twinkle {
      0%, 100% { opacity: 0.3; transform: scale(1); }
      50% { opacity: 1; transform: scale(1.2); }
    }

    @keyframes moonGlow {
      0% { 
        box-shadow: 0 0 30px rgba(255, 215, 0, 0.3),
                    inset -10px -10px 0 rgba(0, 0, 0, 0.1);
      }
      100% { 
        box-shadow: 0 0 50px rgba(255, 215, 0, 0.5),
                    inset -10px -10px 0 rgba(0, 0, 0, 0.1);
      }
    }

    .container {
      max-width: 1200px;
      margin: 0 auto;
      padding: 2rem;
      min-height: 100vh;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      position: relative;
      z-index: 2;
    }

    .header {
      text-align: center;
      margin-bottom: 3rem;
      animation: fadeInUp 1s ease;
    }

    .logo {
      font-size: 3rem;
      font-weight: 300;
      margin-bottom: 0.5rem;
      background: linear-gradient(135deg, var(--accent), var(--accent-hover));
      -webkit-background-clip: text;
      -webkit-text-fill-color: transparent;
      background-clip: text;
    }

    .tagline {
      font-size: 1.1rem;
      color: var(--text-secondary);
      font-weight: 300;
    }

    .calculator-card {
      background: var(--bg-card);
      backdrop-filter: blur(20px);
      border: 1px solid var(--border);
      border-radius: 24px;
      padding: 3rem;
      box-shadow: var(--shadow);
      max-width: 600px;
      width: 100%;
      animation: fadeInUp 1s ease 0.2s both;
    }

    .mode-selector {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 1rem;
      margin-bottom: 2.5rem;
      background: rgba(255, 255, 255, 0.05);
      padding: 0.5rem;
      border-radius: 16px;
    }

    .mode-btn {
      padding: 1rem 1.5rem;
      border: none;
      border-radius: 12px;
      font-size: 1rem;
      font-weight: 500;
      cursor: pointer;
      transition: all 0.3s ease;
      background: transparent;
      color: var(--text-secondary);
    }

    .mode-btn.active {
      background: var(--accent);
      color: white;
      box-shadow: var(--glow);
      transform: translateY(-2px);
    }

    .time-input-section {
      margin-bottom: 2rem;
    }

    .input-label {
      display: block;
      margin-bottom: 1rem;
      font-size: 1.1rem;
      font-weight: 500;
      color: var(--text-primary);
      text-align: center;
    }

    .time-input-wrapper {
      position: relative;
      display: flex;
      justify-content: center;
      margin-bottom: 2rem;
    }

    .time-input {
      font-size: 2.5rem;
      font-weight: 300;
      padding: 1rem 2rem;
      border: 2px solid var(--border);
      border-radius: 16px;
      background: rgba(255, 255, 255, 0.1);
      color: var(--text-primary);
      text-align: center;
      min-width: 200px;
      transition: all 0.3s ease;
    }

    .time-input:focus {
      outline: none;
      border-color: var(--accent);
      box-shadow: var(--glow);
      transform: scale(1.02);
    }

    .calculate-btn {
      width: 100%;
      padding: 1.2rem 2rem;
      font-size: 1.1rem;
      font-weight: 600;
      border: none;
      border-radius: 16px;
      background: linear-gradient(135deg, var(--accent), var(--accent-hover));
      color: white;
      cursor: pointer;
      transition: all 0.3s ease;
      box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
    }

    .calculate-btn:hover {
      transform: translateY(-2px);
      box-shadow: 0 8px 25px rgba(102, 126, 234, 0.6);
    }

    .calculate-btn:active {
      transform: translateY(0);
    }

    .results {
      margin-top: 2rem;
      padding: 2rem;
      background: linear-gradient(135deg, rgba(129, 230, 217, 0.1), rgba(104, 211, 145, 0.1));
      border: 1px solid var(--border);
      border-radius: 20px;
      animation: slideInUp 0.5s ease;
    }

    .results-title {
      font-size: 1.3rem;
      font-weight: 600;
      margin-bottom: 1.5rem;
      text-align: center;
      color: var(--text-primary);
    }

    .time-options {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
      gap: 1rem;
      margin-bottom: 1rem;
    }

    .time-option {
      padding: 1rem;
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: 12px;
      text-align: center;
      font-size: 1.1rem;
      font-weight: 500;
      color: var(--accent);
      transition: all 0.3s ease;
      cursor: pointer;
    }

    .time-option:hover {
      transform: translateY(-2px);
      box-shadow: var(--shadow);
      border-color: var(--accent);
    }

    .cycle-info {
      text-align: center;
      font-size: 0.9rem;
      color: var(--text-secondary);
      margin-top: 1rem;
      font-style: italic;
    }

    .night-mode-toggle {
      position: fixed;
      top: 2rem;
      right: 2rem;
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: 50px;
      padding: 0.8rem 1.5rem;
      cursor: pointer;
      transition: all 0.3s ease;
      backdrop-filter: blur(20px);
      z-index: 100;
    }

    .night-mode-toggle:hover {
      transform: scale(1.05);
      box-shadow: var(--glow);
    }

    .content-section {
      max-width: 800px;
      margin: 4rem auto 2rem;
      padding: 0 2rem;
      animation: fadeInUp 1s ease 0.4s both;
    }

    .info-card {
      background: var(--bg-card);
      backdrop-filter: blur(20px);
      border: 1px solid var(--border);
      border-radius: 20px;
      padding: 2rem;
      margin-bottom: 2rem;
      box-shadow: var(--shadow);
    }

    .info-title {
      font-size: 1.5rem;
      font-weight: 600;
      margin-bottom: 1rem;
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }

    .faq-item {
      margin-bottom: 1rem;
      border: 1px solid var(--border);
      border-radius: 12px;
      overflow: hidden;
    }

    .faq-question {
      padding: 1rem 1.5rem;
      background: rgba(255, 255, 255, 0.02);
      cursor: pointer;
      font-weight: 500;
      transition: all 0.3s ease;
    }

    .faq-question:hover {
      background: rgba(129, 230, 217, 0.1);
    }

    .faq-answer {
      padding: 0 1.5rem;
      max-height: 0;
      overflow: hidden;
      transition: all 0.3s ease;
    }

    .faq-answer.open {
      padding: 1rem 1.5rem;
      max-height: 200px;
    }

    .advice-grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
      gap: 1rem;
      margin-top: 1rem;
    }
    .advice-grid a {
        color: #fff;
    }

    .advice-item {
      padding: 1.5rem;
      background: linear-gradient(135deg, rgba(129, 230, 217, 0.1), rgba(104, 211, 145, 0.1));
      border-radius: 16px;
      border: 1px solid var(--border);
    }

    @keyframes fadeInUp {
      from {
        opacity: 0;
        transform: translateY(30px);
      }
      to {
        opacity: 1;
        transform: translateY(0);
      }
    }

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

    @media (max-width: 768px) {
      .container {
        padding: 1rem;
      }
      
      .calculator-card {
        padding: 2rem;
        margin: 1rem;
      }
      
      .logo {
        font-size: 2.5rem;
      }
      
      .time-input {
        font-size: 2rem;
        min-width: 180px;
      }
      
      .night-mode-toggle {
        top: 1rem;
        right: 1rem;
        padding: 0.6rem 1rem;
      }
    }