/* ==========================================================================
   EMBEDDED SYSTEMS & ROBOTICS HUB - MODERN ENGINEERING STYLESHEET
   ========================================================================== */

:root {
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: 'Fira Code', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Theme: Dark (Default) */
  --bg-primary: #0a0d14;
  --bg-secondary: #121622;
  --bg-tertiary: #192032;
  --bg-card: rgba(25, 32, 50, 0.75);
  --bg-card-hover: rgba(35, 45, 70, 0.85);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-color-hover: rgba(0, 210, 255, 0.3);

  --text-primary: #f0f4fc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --accent-cyan: #00d2ff;
  --accent-blue: #3a86ff;
  --accent-purple: #8338ec;
  --accent-green: #10b981;
  --accent-amber: #f59e0b;
  --accent-red: #ef4444;

  --glow-cyan: 0 0 20px rgba(0, 210, 255, 0.25);
  --glow-purple: 0 0 20px rgba(131, 56, 236, 0.25);

  --header-height: 68px;
  --sidebar-width: 340px;
}

body.light-theme {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;
  --bg-card: #ffffff;
  --bg-card-hover: #f8fafc;
  --border-color: #e2e8f0;
  --border-color-hover: #3a86ff;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;

  --glow-cyan: 0 4px 12px rgba(0, 0, 0, 0.05);
  --glow-purple: 0 4px 12px rgba(0, 0, 0, 0.05);
}

/* Reset & Global */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-main);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header Styles */
.app-header {
  height: var(--header-height);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
}

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

.logo-box {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-icon {
  font-size: 26px;
  filter: drop-shadow(0 0 8px rgba(0, 210, 255, 0.6));
}

.logo-text h1 {
  font-size: 17px;
  font-weight: 800;
  letter-spacing: 0.5px;
  background: linear-gradient(135deg, #00d2ff, #3a86ff, #a855f7);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.logo-text .subtext {
  font-size: 11px;
  color: var(--text-muted);
  font-weight: 500;
  display: block;
  letter-spacing: 0.2px;
}

.header-badge {
  font-size: 11px;
  font-family: var(--font-mono);
  background: rgba(0, 210, 255, 0.1);
  color: var(--accent-cyan);
  padding: 4px 10px;
  border-radius: 20px;
  border: 1px solid rgba(0, 210, 255, 0.25);
}

/* Navigation Tabs */
.app-nav {
  display: flex;
  gap: 6px;
  background: var(--bg-primary);
  padding: 4px;
  border-radius: 12px;
  border: 1px solid var(--border-color);
}

.nav-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: 8px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
}

.nav-btn:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.04);
}

.nav-btn.active {
  background: var(--bg-tertiary);
  color: var(--accent-cyan);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
  border: 1px solid rgba(0, 210, 255, 0.2);
}

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

.progress-pill {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-primary);
  padding: 6px 12px;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  font-size: 12px;
}

.progress-label {
  color: var(--text-muted);
  font-weight: 500;
}

.progress-bar-mini {
  width: 70px;
  height: 6px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 3px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-blue));
  border-radius: 3px;
  transition: width 0.3s ease;
}

.progress-num {
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--accent-cyan);
}

/* Header Interactive Control Buttons (Lang & Theme) */
.header-ctrl-btn {
  display: flex;
  align-items: center;
  gap: 7px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 6px 13px;
  border-radius: 20px;
  cursor: pointer;
  font-size: 12.5px;
  font-weight: 600;
  transition: all 0.25s ease;
  user-select: none;
}

.header-ctrl-btn:hover {
  background: var(--bg-tertiary);
  border-color: var(--accent-cyan);
  box-shadow: 0 0 12px rgba(0, 210, 255, 0.2);
  transform: translateY(-1px);
}

.header-ctrl-btn:active {
  transform: translateY(0);
}

.ctrl-flag, .ctrl-icon {
  font-size: 15px;
  line-height: 1;
}

.ctrl-label {
  font-family: var(--font-mono);
  font-weight: 700;
  letter-spacing: 0.5px;
}

.lang-btn {
  border-color: rgba(0, 210, 255, 0.25);
  background: rgba(0, 210, 255, 0.05);
}

.theme-btn {
  border-color: rgba(168, 85, 247, 0.25);
  background: rgba(168, 85, 247, 0.05);
}

.theme-btn:hover {
  border-color: var(--accent-purple);
  box-shadow: 0 0 12px rgba(168, 85, 247, 0.25);
}

/* Layout: Sidebar + Main Area */
.app-layout {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* Sidebar */
.app-sidebar {
  width: var(--sidebar-width);
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
}

.sidebar-header {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-header h2 {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 10px;
}

.search-box input {
  width: 100%;
  padding: 9px 12px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--text-primary);
  font-size: 13px;
  outline: none;
  transition: border 0.2s;
}

.search-box input:focus {
  border-color: var(--accent-cyan);
}

/* Accordion Level List */
.level-accordion-list {
  flex: 1;
  overflow-y: auto;
  padding: 12px;
}

.level-group {
  margin-bottom: 8px;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  overflow: hidden;
}

.level-header-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 14px;
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  text-align: left;
  transition: background 0.2s;
}

.level-header-btn:hover {
  background: rgba(255, 255, 255, 0.04);
}

.level-header-left {
  display: flex;
  align-items: center;
  gap: 10px;
}

.level-badge {
  font-size: 10px;
  font-family: var(--font-mono);
  background: rgba(0, 210, 255, 0.15);
  color: var(--accent-cyan);
  padding: 2px 7px;
  border-radius: 6px;
  font-weight: 700;
}

.level-progress-ring {
  font-size: 11px;
  color: var(--text-muted);
  font-weight: 600;
}

.lesson-sublist {
  display: none;
  padding: 4px 8px 8px 8px;
  border-top: 1px solid var(--border-color);
  background: rgba(0, 0, 0, 0.15);
}

.level-group.open .lesson-sublist {
  display: block;
}

.level-group.open .level-header-btn {
  background: rgba(255, 255, 255, 0.03);
  border-bottom: 1px solid var(--border-color);
}

.lesson-item-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 9px 12px;
  margin: 3px 0;
  border-radius: 6px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-size: 12.5px;
  cursor: pointer;
  text-align: left;
  transition: all 0.15s ease;
}

.lesson-item-btn:hover {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
}

.lesson-item-btn.active {
  background: rgba(0, 210, 255, 0.12);
  color: var(--accent-cyan);
  font-weight: 600;
  border-left: 3px solid var(--accent-cyan);
}

.lesson-status-icon {
  font-size: 12px;
  margin-left: 8px;
}

/* Main Content Area */
.app-content {
  flex: 1;
  overflow-y: auto;
  position: relative;
}

.tab-pane {
  display: none;
  padding: 32px 48px;
  max-width: 1200px;
  margin: 0 auto;
}

.tab-pane.active {
  display: block;
}

/* Curriculum View */
.lesson-header-banner {
  background: linear-gradient(135deg, rgba(0, 210, 255, 0.08), rgba(131, 56, 236, 0.08));
  border: 1px solid var(--border-color-hover);
  border-radius: 16px;
  padding: 28px 32px;
  margin-bottom: 24px;
  box-shadow: var(--glow-cyan);
}

.lesson-meta-tags {
  display: flex;
  gap: 10px;
  margin-bottom: 12px;
}

.tag-level, .tag-duration, .tag-difficulty {
  font-size: 11px;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--accent-cyan);
}

.lesson-title {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 10px;
  line-height: 1.3;
}

.lesson-desc {
  font-size: 14.5px;
  color: var(--text-secondary);
  max-width: 850px;
}

.lesson-toolbar {
  display: flex;
  gap: 12px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}

.action-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 9px 18px;
  border-radius: 8px;
  border: 1px solid var(--accent-cyan);
  background: var(--accent-cyan);
  color: #050810;
  font-weight: 700;
  font-size: 13px;
  cursor: pointer;
  transition: all 0.2s;
}

.action-btn:hover {
  filter: brightness(1.15);
  box-shadow: 0 0 16px rgba(0, 210, 255, 0.4);
}

.action-btn.secondary {
  background: var(--bg-tertiary);
  border-color: var(--border-color);
  color: var(--text-primary);
}

.action-btn.secondary:hover {
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
}

/* Lesson Markdown Content */
.lesson-body-markdown {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 36px 40px;
  margin-bottom: 40px;
}

.lesson-body-markdown h2 {
  font-size: 20px;
  font-weight: 800;
  margin: 32px 0 16px 0;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 10px;
}

.lesson-body-markdown h2:first-child {
  margin-top: 0;
}

.lesson-body-markdown h3 {
  font-size: 16px;
  font-weight: 700;
  margin: 24px 0 12px 0;
  color: var(--accent-cyan);
}

.lesson-body-markdown p {
  margin-bottom: 16px;
  font-size: 14.5px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.lesson-body-markdown ul, .lesson-body-markdown ol {
  margin: 0 0 18px 24px;
  color: var(--text-secondary);
  font-size: 14px;
}

.lesson-body-markdown li {
  margin-bottom: 8px;
  line-height: 1.6;
}

.lesson-body-markdown strong {
  color: var(--text-primary);
}

/* Code & ASCII Registers */
pre {
  background: #080b12;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 10px;
  padding: 18px 20px;
  overflow-x: auto;
  margin: 20px 0;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.55;
  color: #e2e8f0;
}

code {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: rgba(0, 210, 255, 0.08);
  color: var(--accent-cyan);
  padding: 2px 6px;
  border-radius: 4px;
}

pre code {
  background: transparent;
  padding: 0;
  color: inherit;
}

/* Diagram Cards */
.diagram-box {
  background: #050811;
  border: 1px solid rgba(0, 210, 255, 0.2);
  border-radius: 12px;
  padding: 24px;
  margin: 24px 0;
  text-align: center;
}

.diagram-caption {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 12px;
  font-style: italic;
}

/* Embedded Quiz Section */
.embedded-quiz-section {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 32px;
}

.section-title-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
}

.section-title-bar h2 {
  font-size: 18px;
  font-weight: 800;
  color: var(--text-primary);
}

.quiz-count-badge {
  background: rgba(16, 185, 129, 0.15);
  color: var(--accent-green);
  font-weight: 700;
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 12px;
}

/* Quiz Card Component */
.quiz-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 24px;
  margin-bottom: 20px;
  transition: border-color 0.2s;
}

.quiz-card:hover {
  border-color: rgba(255, 255, 255, 0.15);
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 14px;
}

.quiz-q-num {
  font-size: 11px;
  font-family: var(--font-mono);
  background: rgba(0, 210, 255, 0.1);
  color: var(--accent-cyan);
  padding: 3px 8px;
  border-radius: 6px;
  font-weight: 700;
}

.quiz-category-tag {
  font-size: 11px;
  color: var(--text-muted);
}

.quiz-question-text {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
  line-height: 1.5;
}

.quiz-options-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 16px;
}

.quiz-option-btn {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  font-size: 13.5px;
  cursor: pointer;
  text-align: left;
  transition: all 0.2s;
  position: relative;
}

.quiz-option-btn:hover:not(.locked) {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
  border-color: rgba(0, 210, 255, 0.4);
}

.quiz-option-btn.selected-correct {
  background: rgba(16, 185, 129, 0.15) !important;
  border-color: var(--accent-green) !important;
  color: #34d399 !important;
  font-weight: 600;
}

.quiz-option-btn.selected-wrong {
  background: rgba(239, 68, 68, 0.15) !important;
  border-color: var(--accent-red) !important;
  color: #f87171 !important;
  font-weight: 600;
}

.opt-prefix {
  font-weight: 800;
  font-family: var(--font-mono);
  margin-right: 12px;
  color: var(--accent-cyan);
}

.quiz-explanation-box {
  display: none;
  background: rgba(0, 0, 0, 0.35);
  border-left: 4px solid var(--accent-cyan);
  padding: 14px 18px;
  border-radius: 0 8px 8px 0;
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
}

.quiz-explanation-box.show {
  display: block;
  animation: fadeIn 0.3s ease;
}

.quiz-explanation-box strong {
  color: var(--accent-cyan);
}

/* Quiz Arena Specifics */
.arena-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}

.arena-title-group h1 {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 6px;
}

.arena-filters select {
  padding: 8px 14px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  border-radius: 8px;
  font-size: 13px;
  outline: none;
}

.quiz-score-cards {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-bottom: 32px;
}

.score-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.score-num {
  font-size: 32px;
  font-weight: 900;
  font-family: var(--font-mono);
}

.score-label {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
}

.text-success { color: var(--accent-green); }
.text-primary { color: var(--accent-cyan); }

.reset-quiz-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  padding: 8px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 12px;
  transition: all 0.2s;
}

.reset-quiz-btn:hover {
  border-color: var(--accent-red);
  color: var(--accent-red);
}

/* Simulators Styles */
.sim-header {
  margin-bottom: 24px;
}

.sim-header h1 {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 6px;
}

.sim-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 12px;
  flex-wrap: wrap;
}

.sim-tab-btn {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 9px 18px;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.sim-tab-btn.active {
  background: var(--accent-cyan);
  border-color: var(--accent-cyan);
  color: #050810;
  font-weight: 700;
  box-shadow: 0 0 16px rgba(0, 210, 255, 0.35);
}

.sim-content-pane {
  display: none;
}

.sim-content-pane.active {
  display: block;
}

.sim-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 28px 32px;
}

.sim-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.sim-card-header h3 {
  font-size: 20px;
  font-weight: 800;
}

.sim-desc {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.sim-grid-two {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
}

.sim-controls-panel h4 {
  font-size: 14px;
  margin-bottom: 14px;
  color: var(--accent-cyan);
  text-transform: uppercase;
}

.btn-group-vertical {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 18px;
}

.sim-action-btn {
  padding: 10px 16px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  text-align: left;
  transition: all 0.2s;
}

.sim-action-btn:hover {
  border-color: var(--accent-cyan);
  background: rgba(0, 210, 255, 0.08);
}

.sim-action-btn.secondary {
  border-color: rgba(239, 68, 68, 0.4);
  color: #f87171;
}

.sim-action-btn.secondary:hover {
  background: rgba(239, 68, 68, 0.15);
}

.sim-log-box {
  background: #060910;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 12px;
  height: 160px;
  overflow-y: auto;
  font-family: var(--font-mono);
  font-size: 11.5px;
}

.log-entry {
  margin-bottom: 6px;
  color: var(--text-secondary);
}

.log-entry.system { color: var(--accent-cyan); }
.log-entry.stack { color: #38bdf8; }
.log-entry.heap { color: #f59e0b; }
.log-entry.error { color: #ef4444; font-weight: 700; }

/* Memory Visualizer Canvas/DOM */
.memory-visualizer {
  background: #060812;
  border: 1px solid rgba(0, 210, 255, 0.3);
  border-radius: 12px;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-family: var(--font-mono);
}

.mem-seg {
  border-radius: 6px;
  padding: 12px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 12px;
  font-weight: 700;
  transition: all 0.3s;
}

.seg-stack {
  background: rgba(56, 189, 248, 0.15);
  border: 1px solid #38bdf8;
  color: #38bdf8;
  min-height: 70px;
}

.seg-free-space {
  background: repeating-linear-gradient(45deg, rgba(255,255,255,0.02), rgba(255,255,255,0.02) 10px, transparent 10px, transparent 20px);
  border: 1px dashed rgba(255, 255, 255, 0.15);
  min-height: 45px;
  color: var(--text-muted);
  justify-content: center;
}

.seg-heap {
  background: rgba(245, 158, 11, 0.15);
  border: 1px solid #f59e0b;
  color: #f59e0b;
  min-height: 50px;
}

.seg-bss {
  background: rgba(168, 85, 247, 0.15);
  border: 1px solid #a855f7;
  color: #a855f7;
}

.seg-data {
  background: rgba(16, 185, 129, 0.15);
  border: 1px solid #10b981;
  color: #10b981;
}

.seg-text {
  background: rgba(239, 68, 68, 0.15);
  border: 1px solid #ef4444;
  color: #ef4444;
}

/* GPIO Simulator */
.gpio-sim-workbench {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.register-block h4 {
  font-size: 13px;
  font-family: var(--font-mono);
  color: var(--accent-cyan);
  margin-bottom: 8px;
}

.bitfield-strip {
  display: grid;
  grid-template-columns: repeat(16, 1fr);
  gap: 3px;
  background: #060912;
  padding: 8px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
}

.bit-cell {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 6px 2px;
  text-align: center;
  cursor: pointer;
  transition: all 0.15s;
}

.bit-cell:hover {
  border-color: var(--accent-cyan);
}

.bit-cell.active-bit {
  background: var(--accent-cyan);
  color: #050810;
  font-weight: 800;
}

.bit-num {
  font-size: 9px;
  color: var(--text-muted);
  display: block;
}

.bit-val {
  font-size: 13px;
  font-weight: 700;
  font-family: var(--font-mono);
}

.bit-legend {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 6px;
}

.highlight-text {
  color: var(--accent-cyan);
  font-weight: 700;
}

/* Virtual Breadboard & Circuit */
.virtual-circuit-board {
  background: #111827;
  border: 2px solid #374151;
  border-radius: 12px;
  padding: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  margin-top: 12px;
}

.mcu-chip-visual {
  background: #1f2937;
  border: 2px solid #4b5563;
  border-radius: 6px;
  padding: 16px;
  color: #f3f4f6;
  font-family: var(--font-mono);
  font-size: 12px;
  position: relative;
  text-align: center;
}

.chip-notch {
  width: 14px;
  height: 6px;
  background: #111827;
  border-radius: 0 0 6px 6px;
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
}

.circuit-wire {
  height: 4px;
  width: 50px;
  background: #10b981;
  border-radius: 2px;
  box-shadow: 0 0 8px #10b981;
}

.resistor-visual {
  background: #d97706;
  padding: 6px 12px;
  border-radius: 4px;
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  font-family: var(--font-mono);
}

.virtual-led-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.virtual-led {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: #374151;
  border: 3px solid #4b5563;
  transition: all 0.2s ease;
}

.virtual-led.on {
  background: #10b981;
  border-color: #34d399;
  box-shadow: 0 0 25px #10b981, 0 0 45px #34d399;
}

.led-state-label {
  font-size: 12px;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--accent-green);
}

/* PID Simulator */
.pid-controls {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.slider-control {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 14px;
}

.slider-header {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  font-weight: 700;
  margin-bottom: 6px;
}

.val-display {
  font-family: var(--font-mono);
  color: var(--accent-cyan);
}

.slider-control input[type="range"] {
  width: 100%;
  accent-color: var(--accent-cyan);
  cursor: pointer;
}

.slider-control small {
  display: block;
  font-size: 11px;
  color: var(--text-muted);
  margin-top: 6px;
}

.pid-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
  background: var(--bg-tertiary);
  padding: 12px;
  border-radius: 8px;
  font-size: 11.5px;
}

.pid-canvas-container, .robot-canvas-container, .waveform-canvas-box {
  background: #050811;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  overflow: hidden;
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.canvas-legend {
  display: flex;
  gap: 16px;
  padding: 8px 16px;
  font-size: 12px;
  color: var(--text-muted);
}

.legend-setpoint { color: #ef4444; }
.legend-response { color: #00d2ff; }

/* Robot Kinematics Simulator */
.btn-group-horizontal {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 12px;
}

.odometry-display-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 14px;
  font-size: 13px;
  margin-top: 14px;
}

.odometry-display-box h4 {
  font-size: 12px;
  color: var(--accent-cyan);
  margin-bottom: 8px;
  text-transform: uppercase;
}

.odometry-display-box p {
  margin-bottom: 4px;
  color: var(--text-secondary);
}

/* Waveform Viewer */
.waveform-toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}

.waveform-toolbar select {
  padding: 8px 14px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  border-radius: 8px;
  font-size: 13px;
}

.waveform-explanation {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px;
  margin-top: 16px;
  font-size: 13.5px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Roadmap Grid */
.roadmap-header {
  margin-bottom: 28px;
}

.roadmap-header h1 {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 6px;
}

.roadmap-visual-grid {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.roadmap-stage-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 24px;
  transition: all 0.2s;
}

.roadmap-stage-card:hover {
  border-color: var(--border-color-hover);
  box-shadow: var(--glow-cyan);
}

.stage-card-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.stage-badge {
  font-size: 11px;
  font-family: var(--font-mono);
  font-weight: 800;
  padding: 4px 10px;
  border-radius: 6px;
}

.stage-card-title {
  font-size: 18px;
  font-weight: 800;
  margin-bottom: 8px;
}

.stage-card-desc {
  font-size: 13.5px;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.stage-topics-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.topic-tag {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 12px;
  color: var(--text-secondary);
}

/* Process Timeline */
.process-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 32px;
}

.process-title-group h1 {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 6px;
}

.open-file-btn {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--accent-cyan);
  padding: 9px 16px;
  border-radius: 8px;
  text-decoration: none;
  font-size: 13px;
  font-weight: 600;
  transition: all 0.2s;
}

.open-file-btn:hover {
  background: var(--accent-cyan);
  color: #050810;
}

.process-timeline {
  display: flex;
  flex-direction: column;
  gap: 20px;
  position: relative;
  padding-left: 28px;
}

.process-timeline::before {
  content: '';
  position: absolute;
  top: 10px;
  bottom: 10px;
  left: 8px;
  width: 2px;
  background: var(--border-color);
}

.timeline-entry {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  position: relative;
}

.timeline-entry::before {
  content: '⚡';
  position: absolute;
  left: -28px;
  top: 20px;
  width: 18px;
  height: 18px;
  background: var(--bg-secondary);
  border: 1px solid var(--accent-cyan);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 10px;
}

.timeline-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}

.timeline-date {
  font-size: 12px;
  color: var(--text-muted);
}

.timeline-commit-hash {
  font-family: var(--font-mono);
  font-size: 12px;
  background: rgba(0, 210, 255, 0.1);
  color: var(--accent-cyan);
  padding: 2px 8px;
  border-radius: 4px;
}

.timeline-title {
  font-size: 15px;
  font-weight: 700;
  margin-bottom: 8px;
}

.timeline-details {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Responsive adjustments */
@media (max-width: 900px) {
  .app-layout { flex-direction: column; }
  .app-sidebar { width: 100%; height: 260px; }
  .sim-grid-two { grid-template-columns: 1fr; }
  .quiz-score-cards { grid-template-columns: repeat(2, 1fr); }
  .tab-pane { padding: 20px 16px; }
}