/* Reset */
html, body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: #f4f4f9;
  height: 100%;
  font-size: 16px; /* 1rem = 16px */
}

/* Navigation */
nav {
  background-color: #333;
  padding: 1rem;
  text-align: center;
}

nav a {
  color: white;
  text-decoration: none;
  margin: 0 1rem;
  font-size: 1.1rem;
  font-weight: bold;
}

/* Canvas and Headings */
.canvas {
  margin: 6.25rem auto; /* 100px to rem */
  width: 80%;
  text-align: center;
}

h1 {
  font-size: 2.5rem; /* 40px to rem */
  color: #000000;
  margin-bottom: 1.875rem; /* 30px to rem */
}

h2 {
  font-size: 1.5rem; /* 24px to rem */
  color: #000000;
  margin-top: 1.25rem; /* 20px to rem */
}

/* Color Buttons */
.color-buttons {
  display: flex;
  justify-content: center;
  flex-wrap: wrap; /* Allow wrapping for smaller screens */
  gap: 1.25rem; /* 20px to rem */
}

.button {
  width: 7.5rem; /* 120px to rem */
  height: 7.5rem; /* 120px to rem */
  border-radius: 50%;
  border: none;
  cursor: pointer;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.button:hover {
  transform: scale(1.1);
  box-shadow: 0 0.5rem 1.25rem rgba(0, 0, 0, 0.2); /* 8px 20px */
}

/* Color Definitions */
#grey {
  background-color: #7d7d7d;
}

#white {
  background-color: #ffffff;
  border: 0.0625rem solid #ccc; /* 1px to rem */
}

#blue {
  background-color: #007bff;
}

#yellow {
  background-color: #ffeb3b;
}

/* Smooth background color transition */
body {
  transition: background-color 0.5s ease;
}

/* Responsive Design */
@media (max-width: 48rem) { /* 768px breakpoint */
  h1 {
    font-size: 2rem; /* Adjust heading size */
  }

  h2 {
    font-size: 1.25rem; /* Adjust heading size */
  }

  .color-buttons {
    gap: 1rem; /* Reduce gap for smaller screens */
  }

  .button {
    width: 6rem; /* Reduce button size for smaller screens */
    height: 6rem;
  }

  nav a {
    font-size: 1rem;
  }
}

@media (max-width: 30rem) { /* 480px breakpoint */
  h1 {
    font-size: 1.8rem;
  }

  h2 {
    font-size: 1.1rem;
  }

  .color-buttons {
    gap: 0.625rem; /* Further reduce gap for smaller screens */
  }

  .button {
    width: 5rem; /* Further reduce button size for small devices */
    height: 5rem;
  }

  nav a {
    display: block;
    margin: 0.5rem 0;
  }
}