html,
body {
  min-height: 100%;
}
:root {
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --bg: #f8fafc;
  --card-bg: #fdfefe;
  --text: #0f172a;
  --muted: #64748b;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
  font-family: 'Inter', system-ui, sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: linear-gradient(
    180deg,
    #e5ecfb 0%,
    #e7ecf9 40%,
    #bcdfec 100%
  );
  color: var(--text);
  line-height: 1.6;
}


/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 50;
  padding: 16px 32px;
  background: rgba(15, 23, 42, 0.9);
  backdrop-filter: blur(10px);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo .brand {
  background: linear-gradient(135deg, #3b82f6, #2563eb);
  color: #fff;
  padding: 8px 16px;
  border-radius: 10px;
  font-weight: 700;
  font-size: 18px;
  letter-spacing: 0.5px;
}

.nav {
  display: flex;
  gap: 14px;
}

.nav-btn {
  background: transparent;
  border: 1px solid rgba(255, 255, 255, 0.4);
  color: #fff;
  padding: 8px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 14px;
  transition: all 0.25s ease;
}

.nav-btn:hover {
  background: rgba(255, 255, 255, 0.15);
}

/* ===== Main Container ===== */
.container {
  max-width: 1100px;
  margin: 60px auto;
  padding: 0 20px;
  text-align: center;
}
.container {
  position: relative;
}

.container::before {
  content: "";
  position: absolute;
  inset: -40px;
  background: radial-gradient(circle at top, rgba(37,99,235,0.06), transparent 60%);
  z-index: -1;
}


/* ===== Hero Section ===== */
.hero {
  background: linear-gradient(135deg, #1e3a8a, #2563eb);
  color: #fff;
  padding: 60px 40px;
  border-radius: 20px;
  box-shadow: var(--shadow);
}

.hero h1 {
  font-size: 42px;
  font-weight: 700;
  margin-bottom: 10px;
}

.hero p {
  font-size: 17px;
  color: #e0e7ff;
  max-width: 600px;
  margin: 0 auto 32px;
}

.highlight {
  color: #93c5fd;
}

/* ===== Buttons ===== */
.actions {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 14px;
}

.btn {
  padding: 12px 24px;
  border-radius: 10px;
  border: none;
  cursor: pointer;
  font-size: 14px;
  font-weight: 600;
  background: #ffffff;
  color: #1e3a8a;
  transition: all 0.25s ease;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

/* Primary Button */
.btn.primary {
  background: var(--primary);
  color: white;
}

.btn.primary:hover {
  background: var(--primary-dark);
}

/* ===== Auth Cards ===== */
.card {
  margin-top: 50px;
  background: var(--card-bg);
  padding: 36px;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: flex;
  gap: 40px;
  flex-wrap: wrap;
  justify-content: center;
}

.auth-section {
  flex: 1;
  min-width: 280px;
  text-align: left;
}

.auth-section h3 {
  margin-bottom: 18px;
  font-size: 20px;
}

/* ===== Form Fields ===== */
.field {
  margin-bottom: 18px;
}

.field label {
  display: block;
  margin-bottom: 6px;
  font-size: 13px;
  font-weight: 600;
  color: var(--muted);
}

input,
select {
  width: 100%;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid #cbd5e1;
  font-size: 14px;
  transition: border 0.2s, box-shadow 0.2s;
}

input:focus,
select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.2);
}

/* ===== Small Buttons ===== */
.small-btn {
  padding: 10px 18px;
  border-radius: 8px;
  border: none;
  background: var(--primary);
  color: white;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.small-btn:hover {
  background: var(--primary-dark);
}

/* ===== Courses Grid ===== */
.courses {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 14px;
}

.course-checkbox {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px;
  border-radius: 10px;
  border: 1px solid #e2e8f0;
  background: #f8fafc;
  cursor: pointer;
  transition: all 0.2s ease;
}

.course-checkbox:hover {
  background: #eef2ff;
  border-color: var(--primary);
}

/* ===== Alerts ===== */
.error {
  background: #fee2e2;
  color: #991b1b;
  padding: 12px;
  border-radius: 10px;
  font-size: 13px;
}

.success {
  background: #dcfce7;
  color: #166534;
  padding: 12px;
  border-radius: 10px;
  font-size: 13px;
}

/* ===== Modal ===== */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
}

.modal {
  background: white;
  border-radius: 18px;
  padding: 30px;
  max-width: 480px;
  width: 100%;
  box-shadow: var(--shadow);
}

/* ===== Footer ===== */
.footer {
  margin: 120px 0 30px;
  text-align: center;
  font-size: 13px;
  color: var(--muted);
}