/* Import Fonts from Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Fraunces:ital,opsz,wght@1,9..144,400;600;700;800&family=Inter:wght@300;400;500;600;700&display=swap');


:root {
  --bg-forest: #1E2A1A;
  --bg-forest-light: #2A3B25;
  --bg-forest-dark: #141C11;
  --card-paper: #EFEAD9;
  --card-paper-dark: #E5DFC9;
  --text-dark: #2C362B;
  --text-muted: #5A6458;
  --text-light: #EFEAD9;

  --accent-olive: #8CA05A;
  --accent-olive-dark: #708247;
  --accent-olive-light: #A5B974;
  --accent-clay: #B8814A;
  --accent-clay-dark: #986535;
  --accent-clay-light: #D49D65;

  --node-empty: transparent;
  --node-wall: #2C362B;
  --node-start: #8CA05A;
  --node-end: #B8814A;

  --font-serif: 'Fraunces', serif;
  --font-sans: 'Inter', sans-serif;

  --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow-organic: 0 10px 30px rgba(12, 18, 10, 0.4);
  --shadow-paper: 0 8px 24px rgba(12, 18, 10, 0.15), inset 0 0 40px rgba(0, 0, 0, 0.02);

  /* Touch-friendly minimum tap size */
  --tap-min: 44px;
}

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

html {
  /* Prevent font-size inflation on iOS */
  -webkit-text-size-adjust: 100%;
}

body {
  background-color: var(--bg-forest);
  color: var(--text-light);
  font-family: var(--font-sans);
  min-height: 100vh;
  min-height: 100dvh; /* dynamic viewport for mobile browsers */
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  line-height: 1.5;
}

/* Custom Scrollbar */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg-forest-dark); }
::-webkit-scrollbar-thumb { background: var(--accent-olive); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent-olive-light); }

/* =========================================
   HEADER
   ========================================= */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  padding: 0.9rem 1.5rem;
  background-color: var(--bg-forest-dark);
  border-bottom: 1px solid rgba(140, 160, 90, 0.15);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-shrink: 0;
}

.brand-icon {
  width: 1.8rem;
  height: 1.8rem;
  stroke: var(--accent-olive);
  stroke-width: 1.5;
  fill: none;
  flex-shrink: 0;
}

h1 {
  font-family: var(--font-serif);
  font-weight: 800;
  font-style: italic;
  font-size: clamp(1.1rem, 3.5vw, 1.7rem);
  color: var(--card-paper);
  letter-spacing: -0.5px;
  white-space: nowrap;
}

h1 span { color: var(--accent-olive); }

.nav-tabs {
  display: flex;
  gap: 0.35rem;
  background: var(--bg-forest-light);
  padding: 0.3rem;
  border-radius: 30px;
  border: 1px solid rgba(140, 160, 90, 0.1);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;        /* Firefox */
  flex-shrink: 0;
  max-width: 100%;
}
.nav-tabs::-webkit-scrollbar { display: none; }

.tab-btn {
  background: none;
  border: none;
  color: rgba(239, 234, 217, 0.7);
  padding: 0.55rem 1rem;
  font-family: var(--font-sans);
  font-weight: 500;
  font-size: 0.85rem;
  cursor: pointer;
  border-radius: 20px;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: var(--transition-smooth);
  white-space: nowrap;
  min-height: var(--tap-min);
}

.tab-btn svg { width: 15px; height: 15px; stroke-width: 2; transition: var(--transition-smooth); }
.tab-btn:hover { color: var(--text-light); background-color: rgba(239, 234, 217, 0.05); }
.tab-btn.active { background-color: var(--accent-olive); color: var(--bg-forest); box-shadow: 0 4px 10px rgba(140, 160, 90, 0.2); }
.tab-btn.active svg { stroke: var(--bg-forest); }

/* =========================================
   MAIN LAYOUT
   ========================================= */
main {
  flex: 1;
  display: grid;
  grid-template-columns: 320px 1fr;
  padding: 1.25rem;
  gap: 1.25rem;
  max-width: 1800px;
  width: 100%;
  margin: 0 auto;
}

/* =========================================
   SIDEBAR
   ========================================= */
.sidebar {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

/* =========================================
   PAPER CARDS
   ========================================= */
.paper-card {
  background-color: var(--card-paper);
  color: var(--text-dark);
  border-radius: 14px;
  padding: 1.25rem;
  box-shadow: var(--shadow-paper);
  border: 1px solid rgba(140, 160, 90, 0.15);
  position: relative;
  overflow: hidden;
}

.paper-card::after {
  content: '';
  position: absolute;
  bottom: -20px;
  right: -20px;
  width: 100px;
  height: 100px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%238CA05A' stroke-width='0.5' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M11 20A7 7 0 0 1 9.8 6.1C15.5 5 17 4.48 19 2c1 2 2 3.5 0 8.5C17 15 15 20 11 20z'/%3E%3Cpath d='M19 2c-2.26 4.33-5.27 7.14-8 10'/%3E%3C/svg%3E");
  opacity: 0.08;
  pointer-events: none;
}

.paper-card h2 {
  font-family: var(--font-serif);
  font-weight: 700;
  font-style: italic;
  font-size: 1.25rem;
  margin-bottom: 1rem;
  border-bottom: 1px dashed rgba(44, 54, 43, 0.15);
  padding-bottom: 0.5rem;
  color: var(--text-dark);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.paper-card h2 svg { width: 20px; height: 20px; stroke: var(--accent-olive-dark); stroke-width: 1.75; }

/* Collapsible panel on mobile */
.panel-toggle {
  display: none; /* hidden on desktop */
  width: 100%;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
  text-align: left;
}

.panel-body {
  /* always visible on desktop */
}

/* =========================================
   CONTROLS
   ========================================= */
.control-group { margin-bottom: 1.1rem; }

.control-group label {
  display: block;
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 0.35rem;
  color: var(--text-muted);
}

.select-wrapper { position: relative; }

.select-wrapper select {
  width: 100%;
  padding: 0.7rem 1rem;
  border: 1px solid rgba(44, 54, 43, 0.15);
  border-radius: 8px;
  background-color: rgba(255, 255, 255, 0.45);
  color: var(--text-dark);
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 500;
  appearance: none;
  cursor: pointer;
  transition: var(--transition-smooth);
  min-height: var(--tap-min);
}

.select-wrapper select:focus {
  outline: none;
  border-color: var(--accent-olive-dark);
  background-color: #fff;
  box-shadow: 0 0 0 3px rgba(140, 160, 90, 0.15);
}

.select-wrapper::after {
  content: '▾';
  position: absolute;
  right: 1rem;
  top: 50%;
  transform: translateY(-50%);
  pointer-events: none;
  color: var(--text-muted);
}

/* Sliders */
.slider-container { display: flex; align-items: center; gap: 0.75rem; }

input[type="range"] {
  flex: 1;
  appearance: none;
  height: 6px;
  border-radius: 3px;
  background: rgba(44, 54, 43, 0.1);
  outline: none;
  cursor: pointer;
  /* larger touch area via padding */
  padding: 8px 0;
}

input[type="range"]::-webkit-slider-thumb {
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent-clay);
  transition: var(--transition-smooth);
}

input[type="range"]::-webkit-slider-thumb:hover,
input[type="range"]::-webkit-slider-thumb:active {
  background: var(--accent-clay-dark);
  transform: scale(1.2);
}

.slider-val { font-size: 0.85rem; font-weight: 600; width: 32px; text-align: right; color: var(--text-dark); }

/* Buttons */
.btn-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.65rem;
  margin-top: 0.5rem;
}

.btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  padding: 0.7rem 0.9rem;
  border: none;
  border-radius: 8px;
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.88rem;
  cursor: pointer;
  transition: var(--transition-smooth);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.08);
  min-height: var(--tap-min);
  -webkit-tap-highlight-color: transparent;
}

.btn-primary { background-color: var(--accent-olive); color: var(--bg-forest); }
.btn-primary:hover:not(:disabled) { background-color: var(--accent-olive-dark); transform: translateY(-1px); }
.btn-secondary { background-color: rgba(44, 54, 43, 0.08); color: var(--text-dark); border: 1px solid rgba(44, 54, 43, 0.1); }
.btn-secondary:hover:not(:disabled) { background-color: rgba(44, 54, 43, 0.15); transform: translateY(-1px); }
.btn-accent { background-color: var(--accent-clay); color: white; }
.btn-accent:hover:not(:disabled) { background-color: var(--accent-clay-dark); transform: translateY(-1px); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none !important; }
.btn-full { grid-column: span 2; }

/* Legend */
.legend { display: flex; flex-direction: column; gap: 0.55rem; }
.legend-item { display: flex; align-items: center; gap: 0.7rem; font-size: 0.83rem; font-weight: 500; }
.legend-color {
  width: 18px;
  height: 18px;
  border-radius: 4px;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 10px;
}

/* =========================================
   VISUALIZER AREA
   ========================================= */
.visualizer-container { display: flex; flex-direction: column; gap: 1.25rem; }

.visualizer-card {
  background-color: var(--bg-forest-light);
  border-radius: 14px;
  border: 1px solid rgba(140, 160, 90, 0.15);
  padding: 1rem;
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 380px;
  position: relative;
  box-shadow: var(--shadow-organic);
  overflow: hidden;
}

/* Info Card */
.info-card { background-color: var(--card-paper); color: var(--text-dark); }
.info-content h3 { font-family: var(--font-serif); font-weight: 700; font-style: italic; font-size: 1.05rem; color: var(--accent-clay-dark); margin-bottom: 0.4rem; }
.info-content p { font-size: 0.88rem; color: var(--text-dark); margin-bottom: 0.75rem; line-height: 1.6; }
.complexity-tag {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  font-size: 0.73rem;
  font-weight: 700;
  text-transform: uppercase;
  background-color: rgba(44, 54, 43, 0.06);
  padding: 0.35rem 0.65rem;
  border-radius: 4px;
  margin-top: 0.25rem;
}
.complexity-tag span strong { color: var(--accent-clay-dark); }

/* =========================================
   ALGO VIEWS
   ========================================= */
.algo-view { display: none; width: 100%; height: 100%; animation: fadeIn 0.4s ease-out forwards; }
.algo-view.active { display: flex; flex-direction: column; align-items: center; justify-content: center; }

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

/* =========================================
   PATHFINDING GRID
   ========================================= */
#grid-wrapper {
  width: 100%;
  overflow: auto;
  -webkit-overflow-scrolling: touch;
  display: flex;
  align-items: center;
  justify-content: center;
}

#grid {
  display: grid;
  background-color: rgba(20, 28, 17, 0.6);
  border: 2px solid var(--bg-forest-dark);
  border-radius: 8px;
  overflow: hidden;
  user-select: none;
  touch-action: none;
  /* let JS set width/height explicitly on mobile */
}

.node {
  border: 1px solid rgba(140, 160, 90, 0.08);
  aspect-ratio: 1;
  transition: background-color 0.15s ease-out, transform 0.1s ease-out;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(8px, 1.5vw, 13px);
  font-weight: 700;
  cursor: pointer;
}

.node:hover { background-color: rgba(140, 160, 90, 0.12); }

.node-start { background-color: var(--accent-olive); animation: popStartEnd 0.3s ease-out forwards; color: var(--bg-forest); }
.node-end   { background-color: var(--accent-clay);  animation: popStartEnd 0.3s ease-out forwards; color: white; }
.node-wall  { background-color: var(--node-wall); border-color: var(--bg-forest-dark); animation: growWall 0.25s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards; }
.node-visited        { animation: visitedAnimation 1.2s ease-out forwards; }
.node-shortest-path  { animation: shortestPathAnimation 0.6s cubic-bezier(0.075, 0.82, 0.165, 1) forwards; }

@keyframes growWall {
  0%   { transform: scale(0.3); background-color: var(--bg-forest-dark); border-radius: 30%; }
  100% { transform: scale(1);   background-color: var(--node-wall); }
}
@keyframes popStartEnd {
  0%   { transform: scale(0.5); }
  50%  { transform: scale(1.2); }
  100% { transform: scale(1); }
}
@keyframes visitedAnimation {
  0%   { transform: scale(0.3); background-color: rgba(184,129,74,0.7); border-radius: 100%; }
  40%  { background-color: rgba(140,160,90,0.7); }
  70%  { transform: scale(1.1); background-color: rgba(70,90,60,0.65); }
  100% { transform: scale(1);   background-color: rgba(140,160,90,0.18); border: 1px solid rgba(140,160,90,0.08); }
}
@keyframes shortestPathAnimation {
  0%   { transform: scale(0.4); background-color: var(--accent-clay-light); border-radius: 50%; }
  50%  { transform: scale(1.2); background-color: var(--accent-clay); }
  100% { transform: scale(1);   background-color: var(--accent-clay); box-shadow: 0 0 8px rgba(184,129,74,0.4); }
}

/* Touch hint banner (shown only on touch devices) */
.touch-hint {
  display: none;
  font-size: 0.78rem;
  color: rgba(239, 234, 217, 0.55);
  text-align: center;
  padding: 0.4rem 0;
  font-style: italic;
}

/* =========================================
   SORTING BARS
   ========================================= */
#sorting-container {
  display: flex;
  align-items: flex-end;
  justify-content: center;
  width: 100%;
  height: clamp(220px, 45vw, 380px);
  gap: 2px;
  background-color: rgba(20, 28, 17, 0.4);
  padding: 1rem;
  border-radius: 8px;
  border: 1px solid rgba(140, 160, 90, 0.1);
}

.sorting-bar {
  flex: 1;
  background: var(--accent-olive);
  border-radius: 3px 3px 0 0;
  transition: height 0.05s ease, background-color 0.1s ease;
  min-height: 4px;
}

.bar-compare { background-color: var(--accent-clay)        !important; box-shadow: 0 0 8px rgba(184,129,74,0.6); }
.bar-swap    { background-color: #D49D65                   !important; }
.bar-sorted  { background-color: var(--accent-olive-light) !important; box-shadow: 0 0 6px rgba(140,160,90,0.4); }

/* =========================================
   BACKTRACKING / CHESSBOARD
   ========================================= */
.chessboard-container { display: flex; flex-direction: column; align-items: center; gap: 1rem; width: 100%; }

#chessboard {
  display: grid;
  border: 3px solid var(--node-wall);
  border-radius: 6px;
  overflow: hidden;
  box-shadow: var(--shadow-organic);
  /* JS will set explicit pixel dimensions */
  max-width: 100%;
}

.board-cell {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition-smooth);
}

.cell-light { background-color: var(--card-paper-dark); }
.cell-dark  { background-color: var(--bg-forest-light); }
.cell-queen { animation: placeQueen 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards; }
.queen-icon { width: 70%; height: 70%; fill: var(--accent-clay); stroke: var(--text-dark); stroke-width: 1; }
.cell-threatened { background-color: rgba(184,129,74,0.25); box-shadow: inset 0 0 12px rgba(184,129,74,0.5); }
.cell-success    { background-color: rgba(140,160,90,0.30); box-shadow: inset 0 0 12px rgba(140,160,90,0.6); }

@keyframes placeQueen {
  0%   { transform: scale(0); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}

#backtrack-stats { font-size: 0.88rem; font-style: italic; color: rgba(239,234,217,0.75); text-align: center; }

/* =========================================
   RESPONSIVE BREAKPOINTS
   ========================================= */

/* ---- Tablet landscape → single column ---- */
@media (max-width: 1100px) {
  main {
    grid-template-columns: 1fr;
    padding: 1rem;
  }
  .sidebar { order: 2; }
  .visualizer-container { order: 1; }
}

/* ---- Tablet portrait ---- */
@media (max-width: 768px) {
  header {
    padding: 0.7rem 1rem;
    gap: 0.5rem;
    flex-wrap: wrap;
  }

  .brand-icon { width: 1.5rem; height: 1.5rem; }

  .nav-tabs {
    width: 100%;
    border-radius: 10px;
    padding: 0.25rem;
    gap: 0.25rem;
  }

  .tab-btn {
    flex: 1;
    justify-content: center;
    font-size: 0.8rem;
    padding: 0.5rem 0.6rem;
  }

  /* Show tab icon only, hide text on very small */
  .tab-label { display: none; }

  main { padding: 0.85rem; gap: 1rem; }

  .paper-card { padding: 1rem; border-radius: 12px; }
  .paper-card h2 { font-size: 1.1rem; margin-bottom: 0.75rem; }

  .btn-grid { grid-template-columns: 1fr; gap: 0.55rem; }
  .btn-full { grid-column: span 1; }

  .visualizer-card {
    /* dvh = dynamic viewport height — stays stable even as mobile browser chrome hides */
    height: 60dvh;
    min-height: 320px;
    padding: 0.5rem;
    border-radius: 12px;
    align-items: stretch;   /* let children fill the height */
  }
  #grid-wrapper {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: auto;
    overscroll-behavior: contain; /* prevent page scroll from propagating through grid */
  }

  .touch-hint { display: block; }
}

/* ---- Mobile ---- */
@media (max-width: 480px) {
  h1 { font-size: 1rem; }

  .tab-btn { padding: 0.45rem 0.5rem; font-size: 0.75rem; }

  main { padding: 0.65rem; gap: 0.75rem; }

  .paper-card { padding: 0.85rem; }

  .btn { font-size: 0.85rem; padding: 0.65rem 0.75rem; }

  .visualizer-card {
    /* dvh stays stable when mobile browser chrome hides/shows */
    height: 65dvh;
    min-height: 300px;
    padding: 0.4rem;
  }

  .legend-item { font-size: 0.78rem; }

  #sorting-container { padding: 0.5rem; gap: 1px; }

  .info-content p { font-size: 0.83rem; }
  .complexity-tag { font-size: 0.7rem; }
}

/* Touch-device helpers */
@media (pointer: coarse) {
  /* Larger slider thumb for fingers */
  input[type="range"]::-webkit-slider-thumb { width: 26px; height: 26px; }

  /* Remove hover effects that feel wrong on touch */
  .btn:hover { transform: none; }
  .node:hover { background-color: transparent; }
}