:root {
  --bg-primary: #07120b;      /* Hluboké temně zelené základní pozadí */
  --bg-secondary: #0c1c12;    /* Tmavě lesní zelená pro panely a lišty */
  --bg-tertiary: #132a1c;     /* Mechová zelená pro tlačítka a podklad */
  --bg-elevated: #0f2317;     /* Vyvýšené karty a ovládací prvky */
  --text-main: #e8f7ee;       /* Čitelný mátově bílý text */
  --text-muted: #8eb89f;      /* Jemná šalvějově zelená */
  --text-dim: #547864;        /* Tlumená zelená */
  --accent-primary: #10b981;  /* Zářivý smaragd */
  --accent-hover: #059669;    /* Tmavší smaragd */
  --accent-mint: #34d399;     /* Světlý mátový akcent */
  --accent-linux: #22c55e;
  --accent-win: #10b981;
  --accent-success: #10b981;
  --accent-danger: #ef4444;   /* Výrazná rubínově červená */
  --accent-warning: #f59e0b;
  
  /* Červené akcenty a detaily */
  --accent-red: #ef4444;
  --accent-red-hover: #dc2626;
  --accent-red-bg: #270f12;   /* Temně rudé pozadí pro štítky a chybové karty */
  --accent-red-border: rgba(239, 68, 68, 0.45);
  --accent-red-glow: 0 0 8px rgba(239, 68, 68, 0.4);

  --border-color: #1a3826;    /* Zelené linky a ohraničení */
  --border-subtle: #13291c;
  --border-glow: 0 0 10px rgba(16, 185, 129, 0.25);
  --term-bg: #040a06;         /* Nejhlubší temně zelené terminálové pozadí */
  --term-border: #142e1f;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-main);
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* Scrollbary */
::-webkit-scrollbar {
  width: 7px;
  height: 7px;
}
::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}
::-webkit-scrollbar-thumb {
  background: #1c3d2a;
  border-radius: 4px;
  border: 1px solid #132a1c;
}
::-webkit-scrollbar-thumb:hover {
  background: #2a5a3e;
}

/* Header */
header {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 8px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-shrink: 0;
  height: 52px;
  box-shadow: 0 1px 8px rgba(0, 0, 0, 0.4);
}

.header-left {
  display: flex;
  align-items: center;
  gap: 16px;
}

.logo-area {
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo-icon {
  background: linear-gradient(135deg, #10b981 0%, #059669 100%);
  color: #041208;
  font-family: monospace;
  font-weight: 900;
  font-size: 15px;
  border-radius: 6px;
  width: 30px;
  height: 30px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--accent-red); /* Červený detail orámování */
  box-shadow: 0 0 10px rgba(239, 68, 68, 0.35), 0 0 12px rgba(16, 185, 129, 0.2);
}

.logo-title {
  font-size: 16px;
  font-weight: 700;
  letter-spacing: -0.3px;
  color: var(--text-main);
}

.logo-tag {
  font-size: 11px;
  background: var(--bg-tertiary);
  color: #fca5a5; /* Červený detail textu */
  border: 1px solid var(--accent-red-border); /* Červený detail rámečku */
  padding: 2px 7px;
  border-radius: 12px;
  font-weight: 600;
}

.controls-group {
  display: flex;
  align-items: center;
  gap: 8px;
}

/* Segmented Control pro přepínání OS */
.os-segmented-control {
  display: flex;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 2px;
  gap: 2px;
}

.os-tab-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 5px 12px;
  font-size: 12.5px;
  font-weight: 600;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  gap: 6px;
}

.os-tab-btn:hover {
  color: #fff;
  background: rgba(16, 185, 129, 0.1);
}

.os-tab-btn.active {
  background: var(--bg-tertiary);
  color: #fff;
  box-shadow: 0 1px 3px rgba(0,0,0,0.5);
}

.os-tab-btn.active#os-tab-linux {
  border-bottom: 2px solid var(--accent-red); /* Červený detail aktivní záložky */
}

.os-tab-btn.active#os-tab-windows {
  border-bottom: 2px solid var(--accent-primary);
}

.dropdown-label {
  font-size: 12px;
  color: var(--text-muted);
  font-weight: 600;
  white-space: nowrap;
}

.dropdown {
  background: var(--bg-primary);
  color: var(--text-main);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 5px 10px;
  font-size: 13px;
  outline: none;
  cursor: pointer;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.dropdown:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 6px rgba(16, 185, 129, 0.3);
}

.toolbar {
  display: flex;
  align-items: center;
  gap: 8px;
}

.btn {
  background: var(--bg-tertiary);
  color: var(--text-main);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 6px 12px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.btn:hover {
  background: #1c3d29;
  border-color: var(--accent-primary);
  color: #fff;
}

.btn-primary {
  background: linear-gradient(180deg, #10b981 0%, #059669 100%);
  color: #041409;
  border: 1px solid #10b981;
  font-weight: 700;
}

.btn-primary:hover {
  background: linear-gradient(180deg, #34d399 0%, #10b981 100%);
  color: #020b05;
  box-shadow: 0 0 10px rgba(16, 185, 129, 0.4);
}

.btn-danger {
  background: linear-gradient(180deg, #991b1b 0%, #7f1d1d 100%);
  color: #fee2e2;
  border-color: var(--accent-red);
  box-shadow: 0 0 8px rgba(239, 68, 68, 0.25);
}

.btn-danger:hover {
  background: linear-gradient(180deg, #b91c1c 0%, #991b1b 100%);
  color: #fff;
  box-shadow: 0 0 12px rgba(239, 68, 68, 0.45);
}

/* Hlavní layout (3 panely) */
.main-layout {
  display: flex;
  flex: 1;
  overflow: hidden;
  position: relative;
}

/* Levý panel: Zadání, Teorie, Test */
.panel-instructions {
  width: 340px;
  min-width: 280px;
  max-width: 500px;
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.instructions-header {
  padding: 14px 16px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.status-badge {
  font-size: 11px;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 12px;
}

.status-badge.pending {
  background: var(--accent-red-bg);
  color: #fca5a5;
  border: 1px solid var(--accent-red-border);
}

.status-badge.completed {
  background: #063c22;
  color: #34d399;
  border: 1px solid #059669;
}

.instructions-body {
  padding: 16px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.instructions-title {
  font-size: 17px;
  font-weight: 700;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 6px;
}

.theory-content {
  font-size: 13px;
  line-height: 1.55;
  color: var(--text-main);
}

.theory-content h4 {
  color: #fff;
  margin-bottom: 6px;
  font-size: 14px;
}

.theory-content p {
  margin-bottom: 8px;
}

.theory-content ul, .theory-content ol {
  margin-left: 20px;
  margin-bottom: 8px;
}

.theory-content code {
  background: #05120a;
  color: #34d399;
  padding: 2px 6px;
  border-radius: 4px;
  font-family: monospace;
  font-size: 12px;
  border: 1px solid #142e1f;
}

.theory-box {
  background: #08160e;
  border-left: 3px solid var(--accent-primary);
  border-top: 1px solid var(--border-subtle);
  border-right: 1px solid var(--border-subtle);
  border-bottom: 1px solid var(--border-subtle);
  padding: 10px 12px;
  border-radius: 0 6px 6px 0;
  margin: 10px 0;
  font-size: 12.5px;
  color: var(--text-muted);
}

.task-card {
  background: #07150d;
  border: 1px solid var(--accent-primary);
  box-shadow: inset 0 0 15px rgba(16, 185, 129, 0.06);
  border-radius: 8px;
  padding: 12px 14px;
  position: relative;
}

/* Jemný červený akcentový detail na horním okraji karty úkolu */
.task-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 32px;
  height: 2px;
  background: var(--accent-red);
  border-radius: 8px 0 0 0;
}

.task-card-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--accent-mint);
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.task-card-body {
  font-size: 13px;
  line-height: 1.5;
  color: var(--text-main);
}

.help-actions {
  display: flex;
  gap: 8px;
  margin-top: 6px;
}

.hint-box, .solution-box {
  background: #08150d;
  border: 1px dashed var(--border-color);
  border-radius: 6px;
  padding: 10px;
  font-size: 12px;
  color: var(--text-muted);
}

.solution-box {
  font-family: monospace;
  background: #19090b;
  border-color: var(--accent-red-border);
  color: #fca5a5; /* Červený detail pro řešení */
  white-space: pre-wrap;
}

.instructions-footer {
  padding: 12px 16px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  gap: 8px;
  background: var(--bg-elevated);
}

/* Střední panel: Terminál & nano */
.panel-terminal {
  flex: 1;
  display: flex;
  flex-direction: column;
  background: var(--term-bg);
  position: relative;
  overflow: hidden;
}

/* Pravý panel: Vizuální VFS strom */
.panel-tree {
  width: 320px;
  min-width: 250px;
  max-width: 450px;
  background: var(--bg-secondary);
  border-left: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.tree-header {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.tree-title {
  font-size: 13px;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--text-main);
}

.tree-content {
  flex: 1;
  overflow-y: auto;
  padding: 12px 8px;
}

/* Spodní zápatí / footer */
footer.app-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 5px 16px;
  display: flex;
  flex-direction: column;
  gap: 3px;
  font-size: 11.5px;
  color: var(--text-dim);
  flex-shrink: 0;
  user-select: none;
}

.footer-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  line-height: 1.35;
}

.footer-top {
  border-bottom: 1px solid rgba(26, 56, 38, 0.6);
  padding-bottom: 3px;
}

.footer-bottom {
  padding-top: 1px;
}

.footer-info {
  display: flex;
  align-items: center;
  gap: 7px;
  color: var(--text-muted);
}

.footer-status-indicator {
  display: inline-block;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: #10b981;
  box-shadow: 0 0 8px rgba(16, 185, 129, 0.7);
}

.footer-author {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--text-muted);
  font-size: 11px;
}

.footer-author strong {
  color: var(--text-main);
  font-weight: 600;
}

.footer-sep {
  color: var(--accent-red); /* Červený detail oddělovače v zápatí */
  font-weight: bold;
}

.footer-author-link {
  color: var(--accent-primary);
  text-decoration: none;
  font-weight: 600;
  transition: color 0.15s ease, text-decoration 0.15s ease;
}

.footer-author-link:hover {
  color: var(--accent-red); /* Červený detail na hover autora */
  text-decoration: underline;
}

.footer-meta {
  font-size: 11px;
  color: var(--text-dim);
}

.footer-link {
  color: var(--accent-primary);
  cursor: pointer;
  text-decoration: none;
  font-size: 11.5px;
  font-weight: 500;
  transition: color 0.15s ease;
}

.footer-link:hover {
  color: var(--accent-mint);
  text-decoration: underline;
}

.hidden {
  display: none !important;
}