:root {
  /* Colour palette using CSS variables */
  --clr-bg: #0d1b2a;
  --clr-card: #1b263b;
  --clr-text: #e0f7fa;
  --clr-accent: #5e60ce;
  --clr-accent-shadow: #5e60ceaa;
  --clr-footer: #cdb4db;
}

/* Base Body Styles */
body {
  margin: 0;
  padding: 0;
  font-family: 'Inter', sans-serif;
  background: radial-gradient(circle at top left, #0d1b2a, #000814);
  color: var(--clr-text);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  text-align: center;
  overflow-x: hidden;
}

/* Header styles with theme toggle */
header {
  background-color: var(--clr-card);
  padding: 1rem 0;
  box-shadow: 0 4px 8px rgba(0,0,0,0.3);
  position: relative;
}

.header-content {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 1rem;
  position: relative;
}

#theme-toggle {
  width: 32px;
  height: 32px;
  cursor: pointer;
  transition: transform 0.3s ease;
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
}

#theme-toggle:hover {
  transform: translateY(-50%) rotate(20deg);
}

header h1 {
  margin: 0;
  color: #8ecae6;
  font-size: 2rem;
  letter-spacing: 1px;
}

/* Layout for main content */
main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem 1rem;
}

/* Content card styling */
.card {
  background-color: var(--clr-card);
  padding: 2rem;
  border-radius: 1.5rem;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
  max-width: 400px;
  width: 100%;
}

/* Profile image styles */
.pfp {
  max-width: 90%;
  height: auto;
  margin-bottom: 1rem;
  border-radius: 50%;
  object-fit: cover;
  box-shadow: 0 0 12px rgba(0,0,0,0.4);
}

/* Welcome text */
.welcome {
  font-size: 1.4rem;
  margin-bottom: 1.5rem;
  color: var(--clr-footer);
}

/* Navigation buttons container */
.buttons {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* Universal button styling */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 1.2rem;
  background-color: var(--clr-accent);
  border-radius: 999px;
  transition: all 0.3s ease;
  box-shadow: 0 0 8px var(--clr-accent-shadow);
  font-weight: 600;
  border: none;
  color: white;
  text-decoration: none;
  font-size: 1rem;
}

.btn:hover {
  box-shadow: 0 0 16px var(--clr-accent);
  transform: scale(1.05);
}

/* Disabled button style */
.btn.disabled {
  opacity: 0.6;
  cursor: not-allowed;
  background-color: grey;
  box-shadow: none;
  color: white;
}

/* Footer styles */
footer {
  background-color: var(--clr-card);
  padding: 1rem;
  color: var(--clr-footer);
  font-size: 0.95rem;
  box-shadow: 0 -4px 8px rgba(0, 0, 0, 0.3);
  text-align: center;
  margin-top: auto;
}

.footer-content p {
  margin: 0.2rem 0;
}

.footer-content a {
  color: var(--clr-footer);
  text-decoration: none;
  transition: color 0.3s ease;
}

.footer-content a:hover {
  color: var(--clr-accent);
}

/* Responsive tweaks for small devices */
@media (max-width: 519px) {
  .card {
    padding: 1.5rem;
  }

  .btn {
    font-size: 0.95rem;
    padding: 0.5rem 1rem;
  }

  .welcome {
    font-size: 1.2rem;
  }
}

/* Light mode overrides */
body.light-mode {
  background: radial-gradient(circle at top left, #f0f0f0, #cccccc);
  color: #111;
}

body.light-mode .card,
body.light-mode header,
body.light-mode footer {
  background-color: #ffffff;
  color: #111;
}

body.light-mode .btn {
  background-color: #0077cc;
  box-shadow: 0 0 8px rgba(0, 119, 204, 0.4);
  color: white;
}

body.light-mode .btn:hover {
  box-shadow: 0 0 16px rgba(0, 119, 204, 0.7);
}

body.light-mode header h1 {
  color: #222;
}

body.light-mode .welcome {
  color: #333;
}

body.light-mode .footer-content a {
  color: #222;
}

body.light-mode .footer-content a:hover {
  color: #0077cc;
}