@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@400;700&display=swap');

  body {
    font-family: 'Roboto', sans-serif;
    background: #fff4f4;
    color: #3b1f1f;
    max-width: 700px;
    margin: 2rem auto;
    padding: 1.5rem 1.5rem 3rem;
    border-radius: 10px;
    /* box-shadow: 0 8px 20px rgba(227, 56, 56, 0.25); */
  }

  h1 {
    text-align: center;
    color: #b71c1c;
    font-weight: 700;
    letter-spacing: 1.5px;
    margin-bottom: 1rem;
  }

  .heart-container {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 1rem 0;
    flex-direction: column;
  }

  .heart-icon {
    width: 100px;
    height: 90px;
    margin-bottom: 10px;
    fill: #d32f2f;
    animation: pulse 1s infinite;
    transform-origin: center;
  }

  .heart-rate {
    font-size: 4rem;
    font-weight: 700;
    letter-spacing: 1.2px;
    color: #221d1d;
    min-height: 64px;
    text-shadow: 0 0 8px #f44336aa;
  }

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

  .buttons {
    text-align: center;
    margin: 2rem 0 1rem;
  }

  button {
    background: #b71c1c;
    color: white;
    border: none;
    padding: 0.75rem 1.6rem;
    margin: 0 0.6rem;
    font-size: 1.2rem;
    font-weight: 600;
    cursor: pointer;
    border-radius: 6px;
    box-shadow: 0 5px 15px rgba(183, 28, 28, 0.4);
    transition: background 0.3s ease, box-shadow 0.3s ease;
  }

  button:disabled {
    background: #ef9a9a;
    box-shadow: none;
    cursor: not-allowed;
  }

  button:hover:not(:disabled) {
    background: #7f0000;
    box-shadow: 0 8px 25px rgba(127, 0, 0, 0.7);
  }


  #chart {
    display: block;
    margin: 1rem auto 2rem;
    background: #fff0f0;
    border-radius: 10px;
    box-shadow: inset 0 0 20px #f4433666;
    max-width: 100%;
    height: 140px;
  }

  
  .card {
    background: #fff0f0;
    border-radius: 12px;
    padding: 1rem 1.3rem;
    margin: 1.5rem 0;
    box-shadow: 0 6px 15px rgba(255, 136, 136, 0.15);
    color: #6b2b2b;
  }

  .card h2 {
    margin-top: 0;
    color: #7f1d1d;
    font-weight: 700;
    font-size: 1.5rem;
    border-bottom: 2px solid #d32f2f;
    padding-bottom: 0.3rem;
    margin-bottom: 1rem;
  }

  ul {
    margin-left: 1rem;
  }

  ul li {
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
  }

  p {
    font-size: 1.1rem;
    line-height: 1.5;
  }

  @media (max-width: 480px) {
    .heart-rate {
      font-size: 3rem;
    }
    button {
      font-size: 1rem;
      padding: 0.5rem 1.1rem;
      margin: 0 0.4rem;
    }
  }