/* ==========================================================================
   AI Backend Engineer Intro Animation Styles
   Monochrome, Minimal, High-Precision Cinematic Interface
   Supports Dark and Light Modes with Seamless Theme Switching
   ========================================================================== */

/* Dark Theme (Default) */
.intro-overlay,
.intro-overlay.theme-dark,
html.dark .intro-overlay:not(.theme-light) {
  --intro-bg: #050505;
  --intro-surface: #0a0a0a;
  --intro-text-primary: #F5F5F5;
  --intro-text-secondary: #B0B0B0;
  --intro-text-muted: #777777;
  --intro-text-faint: #292929;
  --intro-border: #292929;
  --intro-border-subtle: #1c1c1c;
  --intro-net-line: #292929;
  --intro-net-line-faint: #181818;
  --intro-net-node-bg: #141414;
  --intro-net-node-border: #737373;
  --intro-net-node-pulse: #F5F5F5;
  --intro-net-flow: #555555;
  --intro-net-flow-rev: #404040;
  --intro-progress-track: #292929;
  --intro-progress-fill: linear-gradient(90deg, #444444 0%, #A0A0A0 60%, #F5F5F5 100%);
  --intro-glow: rgba(255, 255, 255, 0.08);
  --intro-grid: rgba(255, 255, 255, 0.02);
  --intro-vignette: radial-gradient(circle at 50% 50%, transparent 40%, rgba(0, 0, 0, 0.65) 100%);
  --intro-ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  color-scheme: dark;
}

/* Light Theme */
.intro-overlay.theme-light,
html.light .intro-overlay:not(.theme-dark) {
  --intro-bg: #FAFAFA;
  --intro-surface: #FFFFFF;
  --intro-text-primary: #111111;
  --intro-text-secondary: #444444;
  --intro-text-muted: #777777;
  --intro-text-faint: #CCCCCC;
  --intro-border: #E0E0E0;
  --intro-border-subtle: #EBEBEB;
  --intro-net-line: #D0D0D0;
  --intro-net-line-faint: #EAEAEA;
  --intro-net-node-bg: #F0F0F0;
  --intro-net-node-border: #888888;
  --intro-net-node-pulse: #222222;
  --intro-net-flow: #777777;
  --intro-net-flow-rev: #999999;
  --intro-progress-track: #E5E5E5;
  --intro-progress-fill: linear-gradient(90deg, #888888 0%, #444444 60%, #111111 100%);
  --intro-glow: rgba(0, 0, 0, 0.06);
  --intro-grid: rgba(0, 0, 0, 0.035);
  --intro-vignette: radial-gradient(circle at 50% 50%, transparent 50%, rgba(0, 0, 0, 0.04) 100%);
  --intro-ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  color-scheme: light;
}

/* System Light Preference Media Query (Fallback before JS executes) */
@media (prefers-color-scheme: light) {
  .intro-overlay:not(.theme-dark) {
    --intro-bg: #FAFAFA;
    --intro-surface: #FFFFFF;
    --intro-text-primary: #111111;
    --intro-text-secondary: #444444;
    --intro-text-muted: #777777;
    --intro-text-faint: #CCCCCC;
    --intro-border: #E0E0E0;
    --intro-border-subtle: #EBEBEB;
    --intro-net-line: #D0D0D0;
    --intro-net-line-faint: #EAEAEA;
    --intro-net-node-bg: #F0F0F0;
    --intro-net-node-border: #888888;
    --intro-net-node-pulse: #222222;
    --intro-net-flow: #777777;
    --intro-net-flow-rev: #999999;
    --intro-progress-track: #E5E5E5;
    --intro-progress-fill: linear-gradient(90deg, #888888 0%, #444444 60%, #111111 100%);
    --intro-glow: rgba(0, 0, 0, 0.06);
    --intro-grid: rgba(0, 0, 0, 0.035);
    --intro-vignette: radial-gradient(circle at 50% 50%, transparent 50%, rgba(0, 0, 0, 0.04) 100%);
    color-scheme: light;
  }
}

/* Base Fullscreen Overlay */
.intro-overlay {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  height: 100dvh;
  background-color: var(--intro-bg);
  color: var(--intro-text-primary);
  z-index: 999999;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  overflow: hidden;
  user-select: none;
  -webkit-user-select: none;
  opacity: 1;
  visibility: visible;
  transition: opacity 0.4s ease-out, visibility 0.4s ease-out, background-color 0.3s ease, color 0.3s ease;
  cursor: default;
}

.intro-overlay.intro-completed {
  cursor: pointer !important;
}

.intro-overlay.intro-fade-out {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.intro-overlay.intro-hidden {
  display: none !important;
}

/* Subtle background grid pattern for technical depth */
.intro-overlay::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: 
    linear-gradient(to right, var(--intro-grid) 1px, transparent 1px),
    linear-gradient(to bottom, var(--intro-grid) 1px, transparent 1px);
  background-size: 48px 48px;
  pointer-events: none;
  z-index: 0;
}

/* Subtle vignette */
.intro-overlay::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--intro-vignette);
  pointer-events: none;
  z-index: 1;
}

/* Inner Container */
.intro-container {
  position: relative;
  z-index: 2;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  width: 100%;
  height: 100%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 28px 36px;
  box-sizing: border-box;
}

/* ==========================================================================
   A. TOP HEADER
   ========================================================================== */
.intro-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  width: 100%;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--intro-border-subtle);
}

.intro-brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.intro-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--intro-text-secondary);
  font-weight: 500;
  white-space: nowrap;
}

.intro-header-divider {
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--intro-border) 0%, var(--intro-border-subtle) 50%, var(--intro-border) 100%);
}

.intro-status-badge {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--intro-text-muted);
  white-space: nowrap;
}

.intro-status-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--intro-text-secondary);
  box-shadow: 0 0 6px var(--intro-glow);
  animation: introBlink 1.4s infinite ease-in-out;
}

.intro-overlay.intro-completed .intro-status-dot {
  background-color: var(--intro-text-primary);
  animation: none;
}

@keyframes introBlink {
  0%, 100% { opacity: 0.3; transform: scale(0.9); }
  50% { opacity: 1; transform: scale(1.1); }
}

/* ==========================================================================
   B. MAIN CONTENT
   ========================================================================== */
.intro-main {
  flex: 1;
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  align-items: center;
  gap: 48px;
  padding: 24px 0;
  min-height: 0;
}

.intro-left {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 36px;
  max-width: 680px;
}

/* 3-Line Persistent Statement */
.intro-statements {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.intro-statement {
  margin: 0;
  font-family: 'Syne', -apple-system, BlinkMacSystemFont, sans-serif;
  font-size: clamp(2rem, 3.8vw, 3.4rem);
  line-height: 1.12;
  font-weight: 700;
  letter-spacing: -0.035em;
  opacity: 0;
  transform: translateY(18px);
  filter: blur(6px);
  transition: opacity 0.75s var(--intro-ease-out-expo),
              transform 0.75s var(--intro-ease-out-expo),
              filter 0.75s var(--intro-ease-out-expo);
  will-change: transform, opacity, filter;
}

.intro-statement.is-visible {
  opacity: 1;
  transform: translateY(0);
  filter: blur(0);
}

.intro-word-primary {
  color: var(--intro-text-primary);
}

.intro-word-emphasis {
  color: var(--intro-text-secondary);
  font-weight: 600;
}

/* System Status Diagnostics */
.intro-system-status {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  letter-spacing: 0.05em;
  padding-top: 16px;
  border-top: 1px solid var(--intro-border-subtle);
  max-width: 540px;
}

.status-row {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--intro-text-muted);
  opacity: 0;
  transform: translateX(-6px);
  transition: opacity 0.5s ease-out, transform 0.5s ease-out, color 0.3s ease;
}

.status-row.is-active {
  opacity: 1;
  transform: translateX(0);
}

.status-tag {
  color: var(--intro-text-primary);
  font-weight: 700;
  flex-shrink: 0;
}

.status-name {
  color: var(--intro-text-secondary);
  flex-shrink: 0;
  font-size: 11px;
}

.status-dots {
  flex: 1;
  overflow: hidden;
  white-space: nowrap;
  color: var(--intro-text-faint);
  opacity: 0.6;
}

.status-state {
  color: var(--intro-text-muted);
  text-transform: lowercase;
  flex-shrink: 0;
  font-size: 11px;
}

.status-row.is-active .status-state {
  color: var(--intro-text-primary);
}

/* ==========================================================================
   AI NETWORK VISUALIZATION (Monochrome, SVG & CSS)
   ========================================================================== */
.intro-right {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100%;
}

.intro-network-wrapper {
  position: relative;
  width: 100%;
  max-width: 460px;
  aspect-ratio: 1 / 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

.intro-network-svg {
  width: 100%;
  height: 100%;
  overflow: visible;
  filter: drop-shadow(0 0 20px var(--intro-glow));
}

/* Rotating Orbits */
.orbit-rotate-clockwise {
  transform-origin: 250px 250px;
  animation: netOrbitClockwise 28s linear infinite;
}

.orbit-rotate-counter {
  transform-origin: 250px 250px;
  animation: netOrbitCounter 36s linear infinite;
}

.orbit-rotate-slow {
  transform-origin: 250px 250px;
  animation: netOrbitClockwise 48s linear infinite;
}

@keyframes netOrbitClockwise {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

@keyframes netOrbitCounter {
  from { transform: rotate(360deg); }
  to { transform: rotate(0deg); }
}

/* Flowing Dashed Lines */
.network-flow-line {
  stroke: var(--intro-net-flow);
  stroke-width: 1.2;
  stroke-dasharray: 6 8;
  animation: netDashFlow 3.2s linear infinite;
}

.network-flow-line-reverse {
  stroke: var(--intro-net-flow-rev);
  stroke-width: 1;
  stroke-dasharray: 5 7;
  animation: netDashFlowReverse 3.6s linear infinite;
}

@keyframes netDashFlow {
  from { stroke-dashoffset: 28; }
  to { stroke-dashoffset: 0; }
}

@keyframes netDashFlowReverse {
  from { stroke-dashoffset: 0; }
  to { stroke-dashoffset: 24; }
}

/* Pulsing Nodes */
.node-pulse-1 {
  animation: netNodePulse 2.4s ease-in-out infinite;
}
.node-pulse-2 {
  animation: netNodePulse 3s ease-in-out 0.8s infinite;
}
.node-pulse-3 {
  animation: netNodePulse 2.8s ease-in-out 1.6s infinite;
}

@keyframes netNodePulse {
  0%, 100% {
    r: 3.5;
    fill-opacity: 0.5;
    stroke-opacity: 0.3;
  }
  50% {
    r: 5.5;
    fill-opacity: 1;
    stroke-opacity: 0.8;
  }
}

/* Center Core Glow */
.center-core {
  animation: netCorePulse 2.5s ease-in-out infinite;
  transform-origin: 250px 250px;
}

@keyframes netCorePulse {
  0%, 100% {
    transform: scale(0.96);
    opacity: 0.8;
  }
  50% {
    transform: scale(1.05);
    opacity: 1;
  }
}

/* SVG Element Theme Bindings */
.net-ref-ring {
  stroke: var(--intro-net-line-faint);
  stroke-width: 1;
  fill: none;
}

.net-grid-line {
  stroke: var(--intro-net-line-faint);
  stroke-width: 1;
}

.net-orbit-ellipse {
  stroke: var(--intro-net-line);
  stroke-width: 1;
  fill: none;
}

.net-orbit-ellipse-faint {
  stroke: var(--intro-net-line-faint);
  stroke-width: 1;
  fill: none;
}

.net-orbit-dashed {
  stroke: var(--intro-net-line);
  stroke-width: 1;
  fill: none;
}

.net-orbit-node {
  fill: var(--intro-text-secondary);
}

.net-orbit-node-muted {
  fill: var(--intro-text-muted);
}

.net-interconnect {
  stroke: var(--intro-net-line);
  stroke-width: 1;
}

.net-node-outer {
  fill: var(--intro-net-node-bg);
  stroke: var(--intro-net-node-border);
  stroke-width: 1.5;
}

.net-node-outer-accent {
  fill: var(--intro-net-node-bg);
  stroke: var(--intro-text-secondary);
  stroke-width: 1.5;
}

.net-node-pulse {
  fill: var(--intro-net-node-pulse);
  stroke: var(--intro-glow);
  stroke-width: 2;
}

.net-node-pulse-mid {
  fill: var(--intro-text-secondary);
  stroke: var(--intro-glow);
  stroke-width: 2;
}

.net-core-aura {
  fill: var(--intro-glow);
  stroke: var(--intro-border);
  stroke-width: 1;
}

.net-core-shell {
  fill: var(--intro-surface);
  stroke: var(--intro-text-secondary);
  stroke-width: 1.5;
}

.net-core-nucleus {
  fill: var(--intro-text-primary);
}

/* ==========================================================================
   C. PROGRESS BAR & D. FOOTER
   ========================================================================== */
.intro-bottom {
  display: flex;
  flex-direction: column;
  gap: 16px;
  width: 100%;
  padding-top: 16px;
  border-top: 1px solid var(--intro-border-subtle);
}

.intro-progress-wrapper {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
}

.intro-progress-labels {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--intro-text-muted);
}

#intro-progress-num {
  color: var(--intro-text-primary);
  font-weight: 600;
}

.intro-progress-track {
  width: 100%;
  height: 2px;
  background-color: var(--intro-progress-track);
  border-radius: 2px;
  overflow: hidden;
  position: relative;
}

.intro-progress-fill {
  height: 100%;
  width: 0%;
  background: var(--intro-progress-fill);
  box-shadow: 0 0 10px var(--intro-glow);
  transition: width 0.05s linear;
  will-change: width;
}

.intro-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  position: relative;
}

.intro-footer-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--intro-text-muted);
  transition: color 0.3s ease;
}

.intro-overlay.intro-completed .intro-footer-label {
  color: var(--intro-text-secondary);
}

/* Enter Instruction Prompt */
.intro-enter-prompt {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 8px 18px;
  min-height: 44px;
  background-color: var(--intro-surface);
  border: 1px solid var(--intro-border);
  border-radius: 9999px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--intro-text-primary);
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
  transition: opacity 0.5s ease-out, transform 0.5s ease-out, border-color 0.25s ease, background-color 0.25s ease;
  box-shadow: 0 4px 16px var(--intro-glow);
}

.intro-enter-icon {
  font-size: 13px;
  line-height: 1;
  transition: transform 0.2s ease;
}

.intro-overlay.intro-completed .intro-enter-prompt {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
  animation: introPromptPulse 2.6s ease-in-out infinite;
}

.intro-overlay.intro-completed:hover .intro-enter-prompt {
  border-color: var(--intro-text-primary);
}

.intro-overlay.intro-completed:hover .intro-enter-icon {
  transform: translate(2px, -2px);
}

@keyframes introPromptPulse {
  0%, 100% {
    border-color: var(--intro-border);
    box-shadow: 0 4px 12px var(--intro-glow);
  }
  50% {
    border-color: var(--intro-text-secondary);
    box-shadow: 0 4px 20px var(--intro-glow);
  }
}

/* Skip Button */
.intro-skip-btn {
  background: transparent;
  border: 1px solid var(--intro-border);
  color: var(--intro-text-secondary);
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding: 8px 16px;
  min-height: 44px;
  min-width: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 4px;
  cursor: pointer;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease, transform 0.15s ease, opacity 0.3s ease;
}

.intro-skip-btn:hover {
  background-color: var(--intro-surface);
  border-color: var(--intro-text-muted);
  color: var(--intro-text-primary);
}

.intro-skip-btn:focus-visible {
  outline: 2px solid var(--intro-text-primary);
  outline-offset: 2px;
  border-color: var(--intro-text-primary);
}

.intro-skip-btn:active {
  transform: scale(0.97);
}

.intro-overlay.intro-completed .intro-skip-btn {
  opacity: 0;
  pointer-events: none;
  visibility: hidden;
}

/* ==========================================================================
   RESPONSIVE DESIGN (Tablets & Mobile)
   ========================================================================== */

/* Tablets (768px - 1023px) */
@media (max-width: 1023px) {
  .intro-container {
    padding: 24px 28px;
  }

  .intro-main {
    grid-template-columns: 1fr 0.9fr;
    gap: 32px;
  }

  .intro-statement {
    font-size: clamp(1.75rem, 3.2vw, 2.5rem);
  }

  .intro-network-wrapper {
    max-width: 340px;
  }

  .intro-system-status {
    font-size: 11px;
    gap: 6px;
  }
}

/* Mobile Phones (320px - 767px) */
@media (max-width: 767px) {
  .intro-container {
    padding: max(16px, env(safe-area-inset-top)) 16px max(16px, env(safe-area-inset-bottom)) 16px;
    gap: 16px;
  }

  .intro-header {
    padding-bottom: 12px;
    gap: 12px;
  }

  .intro-title {
    font-size: 9.5px;
    letter-spacing: 0.16em;
  }

  .intro-status-badge {
    font-size: 9.5px;
  }

  .intro-main {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: stretch;
    gap: 18px;
    padding: 8px 0;
  }

  .intro-left {
    gap: 16px;
    max-width: 100%;
  }

  .intro-statements {
    gap: 8px;
  }

  .intro-statement {
    font-size: clamp(1.45rem, 6.2vw, 2.05rem);
    line-height: 1.15;
    letter-spacing: -0.025em;
  }

  /* Compact Network on Mobile */
  .intro-right {
    position: relative;
    height: auto;
    max-height: 130px;
    display: flex;
    justify-content: center;
    align-items: center;
    opacity: 0.65;
  }

  .intro-network-wrapper {
    max-width: 130px;
    max-height: 130px;
  }

  .intro-system-status {
    padding-top: 10px;
    gap: 5px;
    font-size: 10px;
  }

  .status-row {
    gap: 6px;
  }

  .status-name {
    font-size: 9.5px;
  }

  .status-dots {
    display: none; /* Hide dots on narrow screens to avoid wrapping */
  }

  .status-state {
    font-size: 9.5px;
    margin-left: auto;
  }

  .intro-bottom {
    padding-top: 10px;
    gap: 12px;
  }

  .intro-footer {
    display: flex;
    flex-direction: column-reverse;
    align-items: center;
    gap: 10px;
  }

  .intro-enter-prompt {
    width: 100%;
    padding: 10px 16px;
    font-size: 10px;
    letter-spacing: 0.1em;
  }

  .intro-footer-label {
    font-size: 9.5px;
    letter-spacing: 0.12em;
  }

  .intro-skip-btn {
    padding: 6px 14px;
    font-size: 10px;
    min-height: 44px;
    width: 100%;
  }
}

/* Extra Narrow Mobile (320px - 360px) */
@media (max-width: 360px) {
  .intro-statement {
    font-size: 1.35rem;
  }

  .intro-right {
    display: none; /* Hide network on extremely small screens to maintain pristine readability */
  }

  .intro-title {
    font-size: 8.5px;
    letter-spacing: 0.12em;
  }
}

/* Mobile Landscape Orientation */
@media (max-height: 520px) and (orientation: landscape) {
  .intro-container {
    padding: 10px 20px;
  }

  .intro-header {
    padding-bottom: 6px;
  }

  .intro-main {
    grid-template-columns: 1.2fr 0.8fr;
    gap: 16px;
    padding: 4px 0;
  }

  .intro-left {
    gap: 8px;
  }

  .intro-statement {
    font-size: 1.25rem;
    line-height: 1.1;
  }

  .intro-network-wrapper {
    max-width: 140px;
    max-height: 140px;
  }

  .intro-system-status {
    padding-top: 6px;
    gap: 4px;
    font-size: 9.5px;
  }

  .intro-bottom {
    padding-top: 6px;
    gap: 6px;
  }

  .intro-skip-btn {
    min-height: 36px;
    padding: 4px 10px;
  }
}

/* ==========================================================================
   REDUCED MOTION SUPPORT
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  .intro-statement {
    transition: opacity 0.2s ease !important;
    transform: none !important;
    filter: none !important;
    opacity: 1 !important;
  }

  .status-row {
    transition: opacity 0.2s ease !important;
    transform: none !important;
    opacity: 1 !important;
  }

  .orbit-rotate-clockwise,
  .orbit-rotate-counter,
  .orbit-rotate-slow,
  .network-flow-line,
  .network-flow-line-reverse,
  .node-pulse-1,
  .node-pulse-2,
  .node-pulse-3,
  .center-core,
  .intro-status-dot,
  .intro-enter-prompt {
    animation: none !important;
  }

  .intro-progress-fill {
    transition: none !important;
  }
}