:root{
  --bg: #f8f9fa;
  --bg-secondary: #ffffff;
  --fg: #212529;
  --muted: #6c757d;
  --card: #ffffff;
  --card-2: #f8f9fa;
  --accent: #0066cc;
  --accent-light: #e7f1ff;
  --accent-2: #28a745;
  --danger: #dc3545;
  --warning: #ffc107;
  --border: #dee2e6;
  --border-light: #e9ecef;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-lg: 0 4px 16px rgba(0,0,0,0.12);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Helvetica Neue", Arial, "Apple Color Emoji", "Segoe UI Emoji";
  line-height: 1.6;
  font-size: 16px;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.site-header {
  padding: 32px 16px 24px;
  text-align: center;
  background: linear-gradient(135deg, var(--accent-light) 0%, var(--bg-secondary) 100%);
  border-bottom: 1px solid var(--border);
}
.site-header h1 {
  margin: 0 0 8px;
  font-size: 32px;
  font-weight: 700;
  color: var(--accent);
}
.subtitle {
  margin: 0 auto;
  max-width: 900px;
  color: var(--muted);
  font-size: 16px;
}

/* layout */
.container{
  max-width: 1100px;
  margin: 0 auto;
  padding: 12px 16px 64px;
}

/* tabs */
.tabs{
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  padding: 6px 0 12px;
  border-bottom: 1px solid var(--border);
}
.tab-button{
  appearance: none;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--fg);
  padding: 10px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s ease;
}
.tab-button:hover{
  background: var(--card-2);
  transform: translateY(-1px);
}
.tab-button.active{
  background: var(--accent);
  color: white;
  border-color: var(--accent);
  box-shadow: 0 2px 8px rgba(0,102,204,0.2);
}

/* panels & cards */
.tab-panel{ display: none; padding-top: 16px; }
.tab-panel.active{ display: block; }

.card{
  background: var(--card);
  border: 1px solid var(--border-light);
  border-radius: 12px;
  padding: 20px;
  box-shadow: var(--shadow);
  margin: 16px 0;
  transition: box-shadow 0.3s ease;
}
.card:hover{
  box-shadow: var(--shadow-lg);
}

.grid-2{
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}
@media (min-width: 880px){
  .grid-2{ grid-template-columns: 1fr 1fr; }
}

/* Playground specific layout - always vertical */
.playground-container{
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 900px;
  margin: 0 auto;
}

.row{
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 8px 0 12px;
}
.row.wrap{ flex-wrap: wrap; }

.label { display:block; margin-bottom: 6px; color: var(--muted); }
.input, textarea, input[type="text"]{
  width: 100%;
  padding: 10px 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  color: var(--fg);
  border-radius: 6px;
  transition: border-color 0.2s ease;
}
.input:focus, textarea:focus, input[type="text"]:focus{
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(0,102,204,0.1);
}
textarea{ resize: vertical; }

.switch input{ margin-right: 6px; }

.btn-row{ display:flex; gap:8px; align-items:center; }
.spacer{ flex:1; }

.btn{
  appearance: none;
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  color: var(--fg);
  padding: 10px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s ease;
}
.btn:hover{ 
  background: var(--card-2);
  transform: translateY(-1px);
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.btn.primary{
  background: var(--accent);
  border-color: var(--accent);
  color: white;
  font-weight: 600;
}
.btn.primary:hover{
  background: #0056b3;
  border-color: #0056b3;
}
.btn.secondary{
  background: var(--accent-light);
  border-color: var(--accent);
  color: var(--accent);
}
.btn.secondary:hover{
  background: #d0e4ff;
}
.btn.tiny{
  padding: 4px 8px;
  font-size: 12px;
  border-radius: 8px;
}

/* chips */
.chip-row{ display:flex; flex-wrap: wrap; gap:8px; margin-bottom: 8px; }
.chip{
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  padding: 8px 14px;
  border-radius: 999px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.2s ease;
}
.chip:hover{
  background: var(--card-2);
  transform: translateY(-1px);
}
.chip.active{
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

/* outputs */
.outputs{
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
}
@media (min-width: 900px){
  .outputs{ grid-template-columns: repeat(2, 1fr); }
}
.out-card{
  background: var(--bg-secondary);
  border: 1px solid var(--border-light);
  border-radius: 10px;
  padding: 14px;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.out-card:hover{
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}
.out-head{
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 6px;
}
.badge{
  display: inline-block;
  padding: 4px 12px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  border: 1px solid transparent;
}
.badge.base64{ 
  background: #e7f1ff; 
  color: #0066cc;
  border-color: #b3d4ff;
}
.badge.base32{ 
  background: #d4edda; 
  color: #155724;
  border-color: #b1dfbb;
}
.badge.base58{ 
  background: #fff3cd; 
  color: #856404;
  border-color: #ffeaa7;
}
.badge.base91{ 
  background: #f8d7da; 
  color: #721c24;
  border-color: #f5c6cb;
}

.out-text{
  background: var(--card-2);
  color: var(--fg);
  padding: 12px;
  border: 1px solid var(--border-light);
  border-radius: 6px;
  min-height: 72px;
  overflow-x: auto;
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
  font-size: 14px;
}
.meta{
  color: var(--muted);
  margin-top: 6px;
  font-size: 13px;
}
.error{ 
  color: var(--danger);
  background: #f8d7da;
  border: 1px solid #f5c6cb;
  padding: 8px 12px;
  border-radius: 6px;
  margin-top: 8px;
}

/* bars */
.bar-legend{ display:flex; gap:8px; margin: 8px 0 12px; }
.bars{ display: grid; gap: 10px; }
.bar-row{ display:grid; grid-template-columns: 120px 1fr 90px; gap:10px; align-items:center; }
.bar-label{ color: var(--muted); }
.bar{
  background: var(--card-2);
  border: 1px solid var(--border-light);
  border-radius: 999px;
  overflow: hidden;
  height: 20px;
}
.bar-fill{ 
  height: 100%; 
  background: linear-gradient(90deg, var(--accent), #4d94ff);
  transition: width 0.3s ease;
}
.bar-fill.base32{ background: linear-gradient(90deg, #28a745, #5cb85c); }
.bar-fill.base58{ background: linear-gradient(90deg, #ffc107, #ffdb4d); }
.bar-fill.base91{ background: linear-gradient(90deg, #dc3545, #ff6b7a); }
.bar-text{ text-align:right; color: var(--muted); }

/* tables */
.table-wrap{ overflow-x:auto; }
table{
  border-collapse: collapse;
  width: 100%;
}
th, td{
  border: 1px solid var(--border);
  padding: 8px 10px;
}
thead th{
  background: var(--card-2);
  font-weight: 600;
  color: var(--accent);
}

/* Special elements */
#alphabetBox{
  background: var(--card-2);
  padding: 16px;
  border-radius: 8px;
  border: 1px solid var(--border-light);
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
  margin: 12px 0;
  color: var(--fg);
}

h3{
  color: var(--accent);
  font-weight: 600;
  margin-top: 20px;
  margin-bottom: 12px;
}

.note{
  color: var(--muted);
  font-size: 14px;
  margin-top: 8px;
}

.bullets{
  padding-left: 20px;
  line-height: 1.8;
}

.bullets li{
  margin: 8px 0;
}

code{
  background: var(--card-2);
  padding: 2px 6px;
  border-radius: 4px;
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
  font-size: 14px;
  color: var(--danger);
}

/* Demo specific styles */
.demo-container{
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.demo-patterns{
  background: var(--card-2);
  padding: 20px;
  border-radius: 8px;
  border: 1px solid var(--border-light);
  margin-bottom: 16px;
}

.demo-patterns h4{
  margin: 0 0 16px 0;
  color: var(--accent);
  font-size: 16px;
}

.pattern-buttons{
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 12px;
}

.pattern-btn{
  background: var(--bg-secondary);
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: left;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.pattern-btn:hover{
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,102,204,0.15);
}

.pattern-btn.active{
  border-color: var(--accent);
  background: var(--accent-light);
}

.pattern-title{
  font-weight: 600;
  color: var(--fg);
  font-size: 14px;
}

.pattern-desc{
  font-size: 12px;
  color: var(--muted);
}

.pattern-info{
  background: var(--accent-light);
  border: 1px solid var(--accent);
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 16px;
}

.pattern-info h4{
  margin: 0 0 8px 0;
  color: var(--accent);
  font-size: 18px;
}

.pattern-info p{
  margin: 0;
  color: var(--fg);
  font-size: 14px;
}

.demo-results{
  background: var(--bg-secondary);
  padding: 16px;
  border-radius: 8px;
  border: 1px solid var(--border-light);
}

.demo-comparison{
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 20px;
}

@media (max-width: 768px){
  .demo-comparison{
    grid-template-columns: 1fr;
  }
}

.comparison-item h4{
  margin: 0 0 8px 0;
  font-size: 14px;
  font-weight: 600;
  text-align: center;
}

.result-box{
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 12px;
}

.result-box.correct{
  border-color: var(--accent-2);
  background: #f0f9f0;
}

.result-box.error{
  border-color: var(--danger);
  background: #fdf2f2;
}

.result-label{
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  margin-bottom: 4px;
}

.result-text{
  background: var(--bg-secondary);
  border: 1px solid var(--border-light);
  border-radius: 4px;
  padding: 8px;
  margin: 4px 0 12px 0;
  font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
  font-size: 13px;
  min-height: 24px;
}

.result-text.decoded{
  font-family: inherit;
  font-weight: 500;
}

.error-text{
  color: var(--danger);
  font-style: italic;
}

/* Character highlighting styles */
.char-highlight{
  padding: 2px 4px;
  border-radius: 3px;
  font-weight: 700;
  position: relative;
}

.char-original{
  background: #e7f1ff;
  color: #0066cc;
  border: 2px solid #b3d4ff;
}

.char-corrupted{
  background: #fdf2f2;
  color: #dc3545;
  border: 2px solid #f5c6cb;
  animation: errorPulse 2s ease-in-out;
}

.char-changed{
  background: #fff3cd;
  color: #856404;
  border: 2px solid #ffeaa7;
}

@keyframes errorPulse {
  0%, 100% { 
    background: #fdf2f2; 
    transform: scale(1);
  }
  50% { 
    background: #f8d7da;
    transform: scale(1.1);
  }
}

.demo-explanation{
  border-top: 1px solid var(--border);
  padding-top: 16px;
}

.demo-explanation h4{
  margin: 0 0 12px 0;
  color: var(--accent);
  font-size: 16px;
}

.comparison-benefits{
  list-style: none;
  padding: 0;
  margin: 0;
}

.comparison-benefits li{
  background: var(--accent-light);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 10px 12px;
  margin: 8px 0;
}

.comparison-benefits strong{
  color: var(--accent);
}

/* Highlight legend styles */
.highlight-legend{
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  align-items: center;
  background: var(--card-2);
  padding: 12px 16px;
  border-radius: 8px;
  margin-bottom: 16px;
  border: 1px solid var(--border-light);
}

.legend-item{
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--fg);
}

/* Practical note styles */
.practical-note{
  background: #e7f1ff;
  border: 1px solid #b3d4ff;
  border-left: 4px solid var(--accent);
  border-radius: 8px;
  padding: 16px;
  margin-top: 16px;
}

.practical-note h5{
  margin: 0 0 8px 0;
  color: var(--accent);
  font-size: 16px;
  font-weight: 600;
}

.practical-note p{
  margin: 0;
  line-height: 1.6;
  font-size: 14px;
}

/* Introduction note styles */
.intro-note{
  background: #fff3cd;
  border: 1px solid #ffeaa7;
  border-left: 4px solid var(--warning);
  border-radius: 6px;
  padding: 12px 16px;
  margin-top: 16px;
  font-size: 14px;
  line-height: 1.5;
}

/* footer */
footer{
  border-top: 1px solid var(--border);
  padding: 16px;
  margin-top: 48px;
  background: var(--bg-secondary);
}
.footer{
  text-align: center;
  color: var(--muted);
  padding: 20px;
}
.footer a{ 
  color: var(--accent);
  font-weight: 500;
  text-decoration: none;
}
.footer a:hover{
  text-decoration: underline;
}