/* Role-based Visibility Control */
.teacher-only { display: none !important; }
.student-only { display: none !important; }

body.role-teacher .teacher-only { display: inline-flex !important; }
body.role-teacher .teacher-only.flex { display: flex !important; }
body.role-teacher .teacher-only.block { display: block !important; }
body.role-teacher .student-only { display: none !important; }

body.role-student .teacher-only { display: none !important; }
body.role-student .student-only { display: inline-flex !important; }
body.role-student .student-only.flex { display: flex !important; }
body.role-student .student-only.block { display: block !important; }

/* Theme Variables (Light Mode Default) */
:root {
  --bg-main: #f8fafc;
  --bg-card: #ffffff;
  --bg-panel: #f1f5f9;
  --bg-sidebar: #ffffff;
  --bg-header: #ffffff;
  --bg-sub: #f8fafc;
  --primary: #0284c7;
  --primary-hover: #0369a1;
  --success: #16a34a;
  --warning: #d97706;
  --danger: #dc2626;
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-dim: #64748b;
  --border: #e2e8f0;
  --border-sub: #cbd5e1;
  --input-bg: #ffffff;
  --code-bg: #f8fafc;
  --code-text: #0284c7;
  --table-th-bg: #f1f5f9;
  --table-border: #e2e8f0;
  --table-hover: rgba(2, 132, 199, 0.05);
  --modal-overlay: rgba(15, 23, 42, 0.6);
  --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px -1px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

[data-theme="dark"] {
  --bg-main: #0b0f19;
  --bg-card: #111827;
  --bg-panel: #1e293b;
  --bg-sidebar: #0f172a;
  --bg-header: #0f172a;
  --bg-sub: #131d31;
  --primary: #38bdf8;
  --primary-hover: #0284c7;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  --border: #334155;
  --border-sub: #1e293b;
  --input-bg: #0f172a;
  --code-bg: #060911;
  --code-text: #38bdf8;
  --table-th-bg: #1e293b;
  --table-border: #1e293b;
  --table-hover: rgba(56, 189, 248, 0.05);
  --modal-overlay: rgba(0, 0, 0, 0.8);
  --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.5);
  --shadow-md: 0 25px 50px -12px rgba(0, 0, 0, 0.6);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg-main);
  color: var(--text-main);
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
  transition: background-color 0.2s ease, color 0.2s ease;
}

/* Button & Form Controls */
.btn {
  background: var(--bg-panel);
  color: var(--text-main);
  border: 1px solid var(--border);
  padding: 0.45rem 0.85rem;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.82rem;
  font-weight: 500;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  transition: all 0.15s ease;
  user-select: none;
}
.btn:hover { background: var(--border); border-color: var(--border-sub); color: var(--text-main); }
.btn-primary { background: var(--primary); color: #ffffff; border-color: var(--primary); font-weight: 600; }
.btn-primary:hover { background: var(--primary-hover); color: #ffffff; border-color: var(--primary-hover); }
.btn-success { background: var(--success); color: #ffffff; border-color: var(--success); font-weight: 600; }
.btn-success:hover { opacity: 0.9; }
.btn-danger { background: rgba(239, 68, 68, 0.12); color: var(--danger); border-color: rgba(239, 68, 68, 0.3); }
.btn-danger:hover { background: var(--danger); color: #ffffff; }

.form-group { margin-bottom: 0.85rem; }
.form-label { display: block; font-size: 0.78rem; font-weight: 600; color: var(--text-muted); margin-bottom: 0.3rem; }
.form-input, .form-select {
  width: 100%;
  background: var(--input-bg);
  border: 1px solid var(--border);
  color: var(--text-main);
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  font-size: 0.85rem;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.form-input:focus, .form-select:focus { border-color: var(--primary); box-shadow: 0 0 0 2px rgba(2, 132, 199, 0.15); }

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.2rem 0.55rem;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--bg-panel);
  color: var(--text-muted);
  border: 1px solid var(--border);
}
.badge-teacher { background: rgba(245, 158, 11, 0.12); color: var(--warning); border: 1px solid rgba(245, 158, 11, 0.3); }
.badge-student { background: rgba(16, 185, 129, 0.12); color: var(--success); border: 1px solid rgba(16, 185, 129, 0.3); }
.badge-lan { background: rgba(2, 132, 199, 0.1); color: var(--primary); border: 1px solid rgba(2, 132, 199, 0.3); }
.dot { width: 6px; height: 6px; border-radius: 50%; background: currentColor; }

/* Modals & Overlays */
.auth-overlay {
  position: fixed;
  inset: 0;
  background: var(--modal-overlay);
  backdrop-filter: blur(8px);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
}
.auth-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  width: 100%;
  max-width: 440px;
  padding: 2rem;
  box-shadow: var(--shadow-md);
  animation: fadeIn 0.2s ease-out;
  position: relative;
}
.auth-brand {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 0.5rem;
}
.auth-brand svg { width: 32px; height: 32px; fill: currentColor; }

.modal-backdrop {
  position: fixed;
  inset: 0;
  background: var(--modal-overlay);
  backdrop-filter: blur(4px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 2000;
}
.modal-backdrop.open { display: flex !important; }
.modal {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  width: 90%;
  max-width: 520px;
  padding: 1.5rem;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-md);
}
.modal h3 { font-size: 1.15rem; color: var(--primary); margin-bottom: 1rem; }

/* Toast */
.toast {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--primary);
  color: var(--text-main);
  padding: 0.75rem 1.25rem;
  border-radius: 8px;
  font-size: 0.85rem;
  box-shadow: var(--shadow-md);
  z-index: 2000;
  display: none;
}

@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }