:root {
  --text: #e8efff;
  --muted: #a2b0d6;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Arial, sans-serif;
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 20% -20%, rgba(56, 88, 197, 0.45), transparent 65%),
    radial-gradient(900px 500px at 90% 10%, rgba(16, 56, 145, 0.28), transparent 60%),
    linear-gradient(180deg, #07133a 0%, #040b23 70%);
}

.container { width: min(1080px, 92%); margin: 0 auto; padding: 22px 0 48px; }

.topbar { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.brand { display: flex; align-items: center; gap: 12px; }
.brand-logo {
  width: 44px;
  height: 44px;
  object-fit: contain;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
  padding: 2px;
}
.brand-title { margin: 0; font-size: 22px; letter-spacing: .3px; }
.brand-subtitle { margin: 2px 0 0; color: var(--muted); font-size: 11px; letter-spacing: 1.3px; }
.teacher-btn {
  border: 1px solid rgba(255,255,255,.2); color: #dbe6ff;
  background: rgba(255,255,255,.03); border-radius: 12px; padding: 10px 14px; font-weight: 600;
}

.hero { margin-top: 26px; }
.chip {
  display: inline-block; padding: 7px 12px; border-radius: 999px;
  background: rgba(37, 82, 187, 0.35); color: #b7d0ff;
  border: 1px solid rgba(97, 134, 220, 0.45); font-size: 13px;
}
.hero h2 { margin: 14px 0 10px; font-size: clamp(28px, 4vw, 46px); }
.hero p { margin: 0; color: var(--muted); max-width: 760px; line-height: 1.6; font-size: 22px; }

.grid { margin-top: 28px; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.card {
  background: linear-gradient(170deg, rgba(18, 36, 84, 0.72), rgba(8, 20, 50, 0.9));
  border: 1px solid rgba(130, 161, 255, 0.18); border-radius: 16px; padding: 18px;
  box-shadow: inset 0 1px 0 rgba(255,255,255,.06);
}
.card-head { display: flex; justify-content: space-between; gap: 12px; }
.card h3 { margin: 0; font-size: 28px; }
.teacher { margin-top: 6px; color: var(--muted); font-size: 22px; }
.badge {
  align-self: flex-start; background: rgba(22, 199, 132, 0.14); color: #5ee7b4;
  border: 1px solid rgba(60, 214, 157, 0.5); padding: 5px 11px; border-radius: 999px; font-size: 13px;
}
.badge-muted {
  background: rgba(184, 196, 224, 0.12);
  color: #c2cde8;
  border-color: rgba(184, 196, 224, 0.35);
}
.desc { color: #a8b8df; margin: 14px 0 16px; min-height: 42px; }
.lesson-time {
  margin: -4px 0 14px;
  color: #c1d0f2;
  font-size: 14px;
}
.card-foot {
  border-top: 1px solid rgba(255,255,255,.12); padding-top: 14px;
  display: flex; justify-content: space-between; align-items: center;
}
.join-link { color: #8db6ff; font-weight: 700; }
.demo-label { color: #ffcc7f; font-size: 13px; }

.upcoming { margin-top: 22px; }
.upcoming h3 { margin-bottom: 10px; }
.upcoming-item {
  background: rgba(255,255,255,.03); border: 1px solid rgba(255,255,255,.1);
  border-radius: 12px; padding: 10px 12px; margin-bottom: 8px;
}
.archive-item {
  opacity: 0.85;
}

.student-card {
  max-width: 980px;
  margin-top: 22px;
}

.join-layout {
  display: grid;
  grid-template-columns: 1.2fr .9fr;
  gap: 22px;
}

.info-panels {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 14px;
}

.info-panel {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 12px;
  padding: 12px;
}

.panel-label {
  display: block;
  color: var(--muted);
  font-size: 12px;
  margin-bottom: 6px;
}

.ok-text {
  color: #5ee7b4;
}

.lesson-extra {
  margin-top: 14px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 12px;
  padding: 12px;
}

.lesson-extra p {
  margin: 0;
  color: #c4d4f6;
}

.join-form-panel {
  background: rgba(8, 18, 47, 0.55);
  border: 1px solid rgba(130, 161, 255, 0.18);
  border-radius: 14px;
  padding: 16px;
}

.join-form-panel h3 {
  margin: 0 0 8px;
}

.join-form {
  margin-top: 14px;
  display: grid;
  gap: 9px;
  max-width: 420px;
}

.join-form label {
  color: #d8e4ff;
  font-weight: 600;
}

.form-input {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(140, 171, 255, 0.35);
  color: #eef4ff;
  border-radius: 10px;
  padding: 11px 12px;
  outline: none;
}

.form-input:focus {
  border-color: #85abff;
  box-shadow: 0 0 0 3px rgba(79, 128, 255, 0.2);
}

.primary-btn {
  margin-top: 6px;
  width: fit-content;
  border: 0;
  border-radius: 10px;
  background: linear-gradient(135deg, #4f8bff, #6f6dff);
  color: #fff;
  font-weight: 700;
  padding: 10px 15px;
  cursor: pointer;
}

.primary-btn:hover {
  filter: brightness(1.06);
}

.field-error,
.form-errors {
  color: #ffb4b4;
  font-size: 13px;
}

a { color: #8eb5ff; text-decoration: none; }
a:hover { text-decoration: underline; }
.muted { color: var(--muted); }

@media (max-width: 900px) {
  .grid { grid-template-columns: 1fr; }
  .hero h2 { font-size: 34px; }
  .hero p, .card h3, .teacher { font-size: 18px; }
  .join-layout { grid-template-columns: 1fr; }
  .info-panels { grid-template-columns: 1fr; }
}