:root {
  --primary-color: #1e88e5; /* Vibrant blue for primary elements */
  --secondary-color: #ff6f61; /* Coral for accents and hover effects */
  --bg-light: #f5f7fa; /* Light background for light mode */
  --bg-dark: #1a1a1a; /* Dark background for dark mode */
  --text-light: #ffffff; /* White text for dark mode */
  --text-dark: #212121; /* Dark text for light mode */
  --card-bg-light: #ffffff; /* White card background for light mode */
  --card-bg-dark: #2a2a2a; /* Dark card background for dark mode */
  --accent-color: #4caf50; /* Green for success states */
  --border-color-light: #ccc; /* Light border for inputs */
  --border-color-dark: #555; /* Dark border for inputs in dark mode */
}

body {
  font-family: 'Roboto', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  margin: 0;
  padding: 0;
  background-color: var(--bg-light);
  color: var(--text-dark);
  transition: all 0.3s ease-in-out;
}

body.dark-mode {
  background-color: var(--bg-dark);
  color: var(--text-light);
}

header {
  background-color: var(--primary-color);
  padding: 1.5rem;
  color: var(--text-light);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
}

.navbar h1 {
  margin: 0;
  font-size: 1.8rem;
}

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text-light);
  font-size: 1.5rem;
  cursor: pointer;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 1.5rem;
  margin: 0;
  padding: 0;
}

.nav-links.active {
  display: flex;
}

.nav-links li a {
  color: var(--text-light);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.3s;
}

.nav-links li a:hover {
  color: var(--secondary-color);
}

.nav-controls {
  display: flex;
  gap: 1rem;
}

#theme-toggle, #view-toggle {
  background-color: var(--secondary-color);
  color: var(--text-light);
  border: none;
  padding: 0.5rem 1rem;
  cursor: pointer;
  border-radius: 5px;
  font-weight: 500;
  transition: background-color 0.3s;
}

#theme-toggle:hover, #view-toggle:hover {
  background-color: #e55a50;
}

main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
  display: grid;
  gap: 2rem;
}

.calculator {
  background-color: var(--card-bg-light);
  padding: 2rem;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  transition: all 0.3s ease-in-out;
}

body.dark-mode .calculator {
  background-color: var(--card-bg-dark);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.calculator h2 {
  margin-top: 0;
  color: var(--primary-color);
  font-size: 1.5rem;
}

.calculator form {
  display: grid;
  gap: 1rem;
}

.input-group {
  display: flex;
  flex-direction: column;
  position: relative;
}

.input-group label {
  font-weight: 500;
  margin-bottom: 0.5rem;
}

input, select {
  padding: 0.75rem;
  border-radius: 5px;
  border: 1px solid var(--border-color-light);
  font-size: 1rem;
  transition: border-color 0.3s, background-color 0.3s;
}

body.dark-mode input, body.dark-mode select {
  border-color: var(--border-color-dark);
  background-color: #333;
  color: var(--text-light);
}

input:focus, select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 5px rgba(30, 136, 229, 0.3);
}

.button-group {
  display: flex;
  gap: 1rem;
}

button {
  background-color: var(--primary-color);
  color: var(--text-light);
  border: none;
  padding: 0.75rem;
  border-radius: 5px;
  cursor: pointer;
  font-size: 1rem;
  transition: background-color 0.3s;
}

button:hover {
  background-color: #1565c0;
}

.advanced-section {
  display: none;
  margin-top: 1rem;
}

body.advanced-mode .advanced-section {
  display: block;
}

.advanced-section p {
  font-size: 0.9rem;
  color: #666;
}

body.dark-mode .advanced-section p {
  color: #bbb;
}

.advanced-section a {
  color: var(--primary-color);
  text-decoration: none;
}

.advanced-section a:hover {
  text-decoration: underline;
}

#bmi-result, #bmr-result, #ideal-result, #bf-result, #tdee-result, #whr-result, #goal-result {
  margin-top: 1rem;
  font-weight: bold;
}

body.dark-mode #bmi-result,
body.dark-mode #bmr-result,
body.dark-mode #ideal-result,
body.dark-mode #bf-result,
body.dark-mode #tdee-result,
body.dark-mode #whr-result,
body.dark-mode #goal-result {
  color: var(--text-light);
}

footer {
  text-align: center;
  padding: 1rem;
  background-color: var(--primary-color);
  color: var(--text-light);
  margin-top: 2rem;
}

footer a {
  color: var(--secondary-color);
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}

/* Mobile Responsive */
@media (max-width: 768px) {
  .hamburger {
    display: block;
  }

  .nav-links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 70px;
    left: 0;
    right: 0;
    background-color: var(--primary-color);
    padding: 1rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  }

  .nav-links.active {
    display: flex;
  }

  .nav-controls {
    flex-direction: column;
    gap: 0.5rem;
  }

  main {
    padding: 1rem;
  }

  .calculator {
    padding: 1.5rem;
  }
}

@media (max-width: 480px) {
  .navbar h1 {
    font-size: 1.5rem;
  }

  .button-group {
    flex-direction: column;
  }

  button {
    width: 100%;
  }

  .calculator h2 {
    font-size: 1.3rem;
  }

  .advanced-section p {
    font-size: 0.85rem;
  }
}