* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
  background: #020617;
  color: #e5e7eb;
}

a {
  color: #38bdf8;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.app-container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1.5rem;
}

.topbar {
  background: #020617;
  border-bottom: 1px solid #1e293b;
  padding: 0.75rem 0;
  margin-bottom: 1.5rem;
}

.topbar-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.1rem;
  font-weight: 700;
}

.topbar nav span {
  margin-right: 1rem;
  font-size: 0.9rem;
  color: #cbd5f5;
}

.topbar nav button {
  margin-left: 0.5rem;
}

button {
  cursor: pointer;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  border: none;
  background: #38bdf8;
  color: #020617;
  font-size: 0.9rem;
  font-weight: 600;
}

.btn-secondary {
  background: #1f2937;
  color: #e5e7eb;
  border: 1px solid #4b5563;
}

.btn:hover {
  background: #0ea5e9;
}

.btn-secondary:hover {
  background: #111827;
}

.card {
  background: #020617;
  border-radius: 0.75rem;
  border: 1px solid #1e293b;
  padding: 1.25rem;
  margin-bottom: 1rem;
}

.card h2 {
  margin-bottom: 0.75rem;
}

.input-group {
  margin-bottom: 0.75rem;
}

.input-group label {
  display: block;
  font-size: 0.85rem;
  margin-bottom: 0.25rem;
  color: #94a3b8;
}

.input-group input {
  width: 100%;
  padding: 0.55rem 0.6rem;
  border-radius: 0.5rem;
  border: 1px solid #1e293b;
  background: #020617;
  color: #e5e7eb;
}

.input-group input:focus {
  outline: none;
  border-color: #38bdf8;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.alert {
  margin-bottom: 1rem;
  padding: 0.75rem 1rem;
  border-radius: 0.5rem;
  font-size: 0.85rem;
}

.alert.error {
  background: #7f1d1d;
  color: #fecaca;
}

.alert.success {
  background: #064e3b;
  color: #bbf7d0;
}

.small {
  font-size: 0.8rem;
  color: #9ca3af;
}

.lesson-list {
  list-style: none;
  margin-top: 0.5rem;
}

.lesson-list li {
  padding: 0.65rem 0;
  border-bottom: 1px solid #1e293b;
}

.lesson-list li:last-child {
  border-bottom: none;
}

.lesson-list a {
  font-size: 0.9rem;
}

.video-wrapper {
  position: relative;
  margin-top: 1rem;
}

.video-wrapper video {
  width: 100%;
  max-width: 900px;
  border-radius: 0.75rem;
  border: 1px solid #1e293b;
  background: black;
  display: block;
}

.watermark {
  position: absolute;
  opacity: 0.25;
  font-size: 1rem;
  color: #ffffff;
  pointer-events: none;
  text-shadow: 1px 1px 3px #000;
  font-weight: 600;
}

.materials-list {
  margin-top: 1rem;
}

.materials-list ul {
  list-style: none;
  margin-top: 0.5rem;
}

.materials-list li {
  padding: 0.4rem 0;
  border-bottom: 1px solid #1e293b;
}

.footer {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid #1e293b;
  text-align: center;
  font-size: 0.8rem;
  color: #6b7280;
}