/* ============================================================================
 * Permutation CipherLab - Stylesheet
 * ============================================================================
 *
 * Design System:
 * - Color palette: Sky blue primary with semantic colors
 * - Typography: System font stack for native feel
 * - Layout: Card-based design with responsive grid
 * - Components: Buttons, inputs, tables, chips, toast notifications
 *
 * Breakpoints:
 * - Mobile: < 768px
 * - Tablet/Desktop: >= 768px
 *
 * ============================================================================ */

/* ============================================================================
 * CSS Custom Properties (Design Tokens)
 * ============================================================================ */
:root{
  /* Color palette */
  --bg:#f6f8fb;               /* Background */
  --card:#ffffff;             /* Card background */
  --text:#0f172a;             /* Primary text */
  --muted:#64748b;            /* Secondary text */
  --primary:#0ea5e9;          /* Primary action color (Sky blue) */
  --primary-ghost:#e0f2fe;    /* Primary tint */
  --border:#e5e7eb;           /* Border color */
  --accent:#10b981;           /* Success/accent (Green) */
  --danger:#ef4444;           /* Error/danger (Red) */
  --shadow:0 8px 24px rgba(0,0,0,0.08); /* Card shadow */
}

/* ============================================================================
 * Base Styles
 * ============================================================================ */
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  font-family: ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,Apple Color Emoji,Segoe UI Emoji;
  color:var(--text);
  background:var(--bg);
  line-height:1.6;
}

/* ============================================================================
 * Layout Components
 * ============================================================================ */

/* App Header */
.app-header{
  padding:24px 16px 8px;
  text-align:center;
}
.app-header h1{margin:0 0 6px 0; font-size:28px;}
.subtitle{margin:0; color:var(--muted)}

/* Tab Navigation */
.tabs{
  display:flex;
  gap:8px;
  justify-content:center;
  padding:8px 12px 16px;
  flex-wrap:wrap;
}
.tab{
  border:1px solid var(--border);
  background:#fff;
  padding:8px 14px;
  border-radius:999px;
  cursor:pointer;
  color:var(--muted);
  transition: all 0.15s ease;
}
.tab.active{
  background:var(--primary);
  color:#fff;
  border-color:transparent;
}

/* Main Content Area */
main{max-width:1100px; margin:0 auto; padding:0 16px 24px;}
.panel{display:none}
.panel.active{display:block}

/* Grid Layout (2-column for encryption/decryption tabs) */
.grid{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:16px;
}

/* ============================================================================
 * Responsive Design
 * ============================================================================ */
@media (max-width:768px){
  .grid{grid-template-columns:1fr}
  .row{flex-direction:column; align-items:flex-start}
  .row label{min-width:auto; margin-bottom:4px}
  .drag-list{flex-wrap:wrap}
  /* Keep horizontal layout for keygen buttons even on mobile */
  .method-card .row, .key-management .row{
    flex-direction:row;
    align-items:center;
  }
}

/* ============================================================================
 * Card Component
 * ============================================================================ */
.card{
  background:var(--card);
  border:1px solid var(--border);
  border-radius:16px;
  padding:16px;
  box-shadow:var(--shadow);
}

/* Typography */
h2{margin-top:4px}
h3{margin-top:16px}

/* ============================================================================
 * Form Elements
 * ============================================================================ */

/* Text inputs and textareas */
textarea,input[type=text],input[type=number]{
  width:100%;
  border:1px solid var(--border);
  background:#fff;
  border-radius:10px;
  padding:10px 12px;
  font-size:14px;
  color:var(--text);
  outline:none;
  transition: all 0.15s ease;
}
textarea{resize:vertical}
textarea[readonly]{
  background:#f8fafc;
  color:var(--muted);
  cursor:not-allowed;
}
input:focus, textarea:focus{
  outline:2px solid var(--primary);
  outline-offset:2px;
}

/* Form row layout */
.row{
  display:flex;
  gap:10px;
  align-items:center;
  margin:10px 0;
  position:relative;
}
.row label{min-width:110px; color:var(--muted)}
.checkbox{display:flex; align-items:center; gap:8px; color:var(--muted)}

/* Error messages */
.error-msg{
  color:var(--danger);
  font-size:12px;
  margin-top:4px;
  display:block;
  animation: fadeIn 0.2s ease;
}
@keyframes fadeIn{
  from{opacity:0; transform:translateY(-4px)}
  to{opacity:1; transform:translateY(0)}
}

/* ============================================================================
 * Buttons
 * ============================================================================ */

/* Action button container */
.actions{display:flex; gap:10px; flex-wrap:wrap; margin-top:12px}
@media (max-width:480px){
  .actions{flex-direction:column}
  .actions .btn{width:100%}
}

/* Base button style */
.btn{
  border:1px solid var(--border);
  background:#fff;
  color:var(--text);
  padding:8px 14px;
  border-radius:10px;
  cursor:pointer;
  transition: all 0.15s ease;
}
.btn:hover{
  background:#f8fafc;
  border-color:var(--muted);
}
.btn:focus{
  outline:2px solid var(--primary);
  outline-offset:2px;
}
.btn.primary{
  background:var(--primary);
  border-color:var(--primary);
  color:#fff;
}
.btn.primary:hover{
  background:#0284c7;
  border-color:#0284c7;
}
.btn.ghost{
  background:var(--primary-ghost);
  color:#0369a1;
  border-color:transparent;
}
.btn.ghost:hover{
  background:#bae6fd;
}

.table-wrap{overflow:auto; border:1px solid var(--border); border-radius:12px}
.map-table{
  width:100%;
  border-collapse:collapse;
  font-size:14px;
}
.map-table th,.map-table td{
  padding:8px 10px;
  border-bottom:1px solid var(--border);
  text-align:left;
}
.map-table thead th{background:#f8fafc; color:var(--muted); font-weight:600;}
.map-table tbody tr:nth-child(even){background:#f1f5f9}
.map-table tbody tr:hover{background:#e0f2fe}

.saved-list{
  display:flex; flex-wrap:wrap; gap:8px; margin-top:8px;
  max-height:120px;
  overflow-y:auto;
  padding:4px;
}
.saved-list .chip{
  display:inline-flex; gap:6px; align-items:center;
  border:1px solid var(--border); padding:6px 10px; border-radius:999px; background:#fff;
  transition: all 0.15s ease;
}
.saved-list .chip:hover{
  border-color:var(--primary);
  box-shadow:0 2px 8px rgba(14,165,233,0.15);
}
.saved-list .chip button{
  border:none; background:transparent; color:var(--muted); cursor:pointer;
  transition: color 0.15s ease;
}
.saved-list .chip button:hover{
  color:var(--primary);
}
.saved-list .chip button:last-child:hover{
  color:var(--danger);
}

.pad-opts summary{cursor:pointer; color:var(--muted); margin:8px 0}
.pad-note{
  margin:8px 0 0;
  font-size:12px;
  color:var(--muted);
  line-height:1.5;
}

.input-with-preset{
  position:relative;
}
.preset-control{
  margin-top:8px;
  position:relative;
}
.btn-sm{
  padding:6px 12px;
  font-size:13px;
}
.preset-list{
  margin-top:8px;
  background:#fff;
  border:1px solid var(--border);
  border-radius:8px;
  padding:8px;
  display:flex;
  flex-direction:column;
  gap:6px;
  max-height:200px;
  overflow-y:auto;
}
.preset-item{
  border:1px solid var(--border);
  background:#fff;
  color:var(--text);
  padding:8px 12px;
  border-radius:6px;
  cursor:pointer;
  text-align:left;
  font-size:13px;
  transition:all 0.15s ease;
  white-space:nowrap;
  overflow:hidden;
  text-overflow:ellipsis;
}
.preset-item:hover{
  background:var(--primary-ghost);
  border-color:var(--primary);
  color:var(--primary);
}

.block-nav{
  display:flex;
  align-items:center;
  justify-content:center;
  gap:12px;
  margin:12px 0;
  padding:8px;
  background:#f8fafc;
  border-radius:8px;
}
.block-indicator{
  font-size:14px;
  font-weight:600;
  color:var(--text);
  min-width:100px;
  text-align:center;
}

#panel-study .card{
  line-height:1.8;
  max-width:1000px;
  margin:0 auto;
}
#panel-study h2{
  margin-top:8px;
  margin-bottom:16px;
  font-size:24px;
  text-align:center;
  color:var(--text);
}
#panel-study h3{
  margin-top:24px;
  margin-bottom:12px;
  color:var(--primary);
  font-size:20px;
  border-bottom:2px solid var(--primary-ghost);
  padding-bottom:8px;
}
#panel-study h4{
  margin:12px 0 8px;
  font-size:16px;
  color:var(--text);
}
#panel-study p{
  margin:12px 0;
}
#panel-study ul{
  margin:12px 0;
  padding-left:24px;
  line-height:1.8;
}
#panel-study code{
  background:#f1f5f9;
  padding:2px 6px;
  border-radius:4px;
  font-family:'Courier New', monospace;
  font-size:13px;
  color:#0369a1;
}

.study-content{
  padding:24px;
}
.study-intro{
  font-size:16px;
  background:var(--primary-ghost);
  padding:16px;
  border-radius:8px;
  border-left:4px solid var(--primary);
  margin-bottom:24px;
}
.study-section{
  margin:32px 0;
}

/* Study Accordion */
.study-accordion{
  border:1px solid var(--border);
  border-radius:8px;
  background:#fff;
  margin:16px 0;
}
.study-accordion summary{
  cursor:pointer;
  padding:12px 16px;
  user-select:none;
  transition:all 0.15s ease;
  list-style:none;
}
.study-accordion summary::-webkit-details-marker{
  display:none;
}
.study-accordion summary::before{
  content:'▶';
  display:inline-block;
  width:20px;
  transition:transform 0.15s ease;
  color:var(--primary);
}
.study-accordion[open] summary::before{
  transform:rotate(90deg);
}
.study-accordion summary:hover{
  background:#f8fafc;
}
.study-accordion summary h3{
  display:inline;
  margin:0;
  font-size:18px;
}
.study-accordion > *:not(summary){
  padding:0 16px 16px 16px;
}

/* Timeline */
.timeline{
  margin:16px 0;
  padding-left:20px;
  border-left:3px solid var(--primary);
}
.timeline-item{
  margin:16px 0;
  padding:12px 16px;
  background:#f8fafc;
  border-radius:8px;
  position:relative;
}
.timeline-item::before{
  content:'';
  position:absolute;
  left:-28px;
  top:20px;
  width:12px;
  height:12px;
  border-radius:50%;
  background:var(--primary);
  border:3px solid #fff;
}
.timeline-item strong{
  color:var(--primary);
  font-size:14px;
  display:block;
  margin-bottom:6px;
}

/* Example box */
.example-box{
  background:#fff9e6;
  border:2px solid #ffc107;
  border-radius:8px;
  padding:16px;
  margin:16px 0;
}
.example-table{
  width:100%;
  max-width:400px;
  margin:12px auto;
  border-collapse:collapse;
}
.example-table th,
.example-table td{
  padding:8px 12px;
  text-align:center;
  border:1px solid var(--border);
}
.example-table th{
  background:#f8fafc;
  font-weight:600;
}
.example-table .arrow-row td{
  color:var(--primary);
  font-weight:bold;
  background:#f0f9ff;
}
.example-box .result{
  text-align:center;
  font-size:15px;
  margin-top:12px;
  padding-top:12px;
  border-top:1px solid #ffc107;
}

/* Comparison box */
.comparison-box{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:16px;
  margin:16px 0;
}
@media (max-width:768px){
  .comparison-box{
    grid-template-columns:1fr;
  }
}
.compare-item{
  background:#f8fafc;
  border:2px solid var(--border);
  border-radius:8px;
  padding:16px;
}
.compare-item ul{
  margin:8px 0;
  padding-left:20px;
}
.compare-item .note{
  font-size:13px;
  color:var(--muted);
  font-style:italic;
  margin-top:8px;
}

/* Comparison table */
.comparison-table{
  width:100%;
  border-collapse:collapse;
  margin:16px 0;
  font-size:14px;
}
.comparison-table th,
.comparison-table td{
  padding:10px 12px;
  border:1px solid var(--border);
  text-align:left;
}
.comparison-table thead th{
  background:var(--primary-ghost);
  color:var(--primary);
  font-weight:600;
}
.comparison-table tbody td:first-child{
  background:#f8fafc;
  font-weight:600;
}

/* Strength & Weakness */
.strength-weakness{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:16px;
  margin:16px 0;
}
@media (max-width:768px){
  .strength-weakness{
    grid-template-columns:1fr;
  }
}
.strength, .weakness{
  border-radius:8px;
  padding:16px;
}
.strength{
  background:#e6f7ed;
  border:2px solid var(--accent);
}
.weakness{
  background:#fee;
  border:2px solid var(--danger);
}
.strength h4{
  color:var(--accent);
  margin-top:0;
}
.weakness h4{
  color:var(--danger);
  margin-top:0;
}

/* Educational list */
.educational-list{
  list-style:none;
  padding:0;
}
.educational-list li{
  padding:12px 16px;
  margin:8px 0;
  background:#f0f9ff;
  border-left:4px solid var(--primary);
  border-radius:4px;
}

/* Related ciphers */
.related-ciphers{
  display:grid;
  grid-template-columns:repeat(auto-fit, minmax(200px, 1fr));
  gap:16px;
  margin:16px 0;
}
.cipher-card{
  background:#f8fafc;
  border:1px solid var(--border);
  border-radius:8px;
  padding:16px;
  transition:all 0.15s ease;
}
.cipher-card:hover{
  border-color:var(--primary);
  box-shadow:0 4px 12px rgba(14,165,233,0.15);
}
.cipher-card h4{
  color:var(--primary);
  margin-top:0;
}
.cipher-card p{
  font-size:13px;
  color:var(--muted);
  margin:8px 0 0;
}

/* Reference list */
.reference-list{
  list-style:none;
  padding:0;
}
.reference-list li{
  padding:10px 16px;
  margin:8px 0;
  background:#f8fafc;
  border-radius:6px;
  border-left:3px solid var(--primary);
}

/* Key Generation Tab */
.keygen-card{
  max-width:900px;
  margin:0 auto;
}
.keygen-card .description{
  color:var(--muted);
  margin:8px 0 16px;
}
.keygen-methods{
  margin:24px 0;
}
.method-card{
  background:#f8fafc;
  border:1px solid var(--border);
  border-radius:12px;
  padding:16px;
  margin:16px 0;
}
.method-card h4{
  margin:0 0 8px 0;
  color:var(--text);
}
.method-card p{
  margin:4px 0 12px;
  color:var(--muted);
  font-size:14px;
}
.method-card .row{
  flex-direction:row;
  align-items:center;
}
.method-card .row input{
  flex:1;
}
.method-card .row .btn{
  flex-shrink:0;
  width:auto;
}
.current-key{
  background:#f0f9ff;
  border:2px solid var(--primary);
  border-radius:12px;
  padding:16px;
  margin:24px 0;
}
.current-key h3{
  margin-top:0;
}
.key-display{
  display:flex;
  align-items:center;
  gap:12px;
  margin:12px 0;
}
.key-text{
  font-family:'Courier New', monospace;
  font-size:18px;
  font-weight:bold;
  color:var(--primary);
  background:#fff;
  padding:8px 16px;
  border-radius:8px;
  flex:1;
}
.key-info{
  margin:8px 0 0;
  font-size:13px;
  color:var(--muted);
}
.key-visualization{
  margin-top:20px;
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:16px;
}
@media (max-width:768px){
  .key-visualization{
    grid-template-columns:1fr;
  }
}
.viz-section{
  background:#fff;
  border:1px solid var(--border);
  border-radius:8px;
  padding:12px;
  overflow-x:auto;
}
.viz-section h4{
  margin:0 0 12px 0;
  font-size:14px;
  color:var(--text);
  text-align:center;
}
.pattern-viz{
  display:flex;
  flex-direction:column;
  align-items:center;
  gap:8px;
  min-width:min-content;
}
.viz-row{
  display:flex;
  gap:8px;
  align-items:center;
}
.viz-cell{
  width:40px;
  height:40px;
  display:flex;
  align-items:center;
  justify-content:center;
  font-family:'Courier New', monospace;
  font-size:16px;
  font-weight:bold;
  border:2px solid var(--border);
  border-radius:6px;
  background:#fff;
}
.viz-cell.top{
  background:#f8fafc;
  color:var(--muted);
}
.viz-cell.bottom{
  background:var(--primary-ghost);
  color:var(--primary);
}
.viz-arrows{
  display:flex;
  gap:8px;
}
.viz-arrow{
  width:40px;
  display:flex;
  flex-direction:column;
  align-items:center;
  color:var(--primary);
  font-size:20px;
}
.key-management{
  margin:24px 0;
}
.key-management .row{
  flex-direction:row;
  align-items:center;
}
.key-management .row input{
  flex:1;
}
.key-management .row .btn{
  flex-shrink:0;
  width:auto;
}
.key-info-box{
  background:#f8fafc;
  border:1px solid var(--border);
  border-radius:8px;
  padding:12px;
  margin:12px 0;
  font-size:14px;
  line-height:1.8;
}
.key-info-box strong{
  color:var(--text);
}
.key-info-box span{
  color:var(--muted);
  font-family:'Courier New', monospace;
}
.block-size-info{
  font-size:13px;
  color:var(--primary) !important;
  font-weight:600;
}
.pattern-length-info{
  background:#fff9e6;
  border:1px solid #ffc107;
  border-radius:8px;
  padding:16px;
  margin:12px 0;
}
.length-section{
  margin-bottom:12px;
}
.length-section > label{
  display:block;
  font-weight:600;
  margin-bottom:10px;
  color:var(--text);
}
.length-controls{
  display:flex;
  align-items:center;
  gap:12px;
  flex-wrap:wrap;
}
.length-controls input{
  width:80px;
  padding:6px 10px;
  font-size:14px;
}
.preset-group{
  display:flex;
  align-items:center;
  gap:8px;
  flex-wrap:wrap;
}
.preset-label{
  font-size:13px;
  color:var(--muted);
  white-space:nowrap;
}
.preset-buttons{
  display:flex;
  gap:6px;
  flex-wrap:wrap;
}
.btn-preset{
  border:2px solid var(--border);
  background:#fff;
  color:var(--text);
  padding:6px 14px;
  border-radius:8px;
  cursor:pointer;
  font-weight:600;
  font-size:13px;
  transition:all 0.15s ease;
  min-width:44px;
}
.btn-preset:hover{
  border-color:var(--primary);
  background:#f0f9ff;
  color:var(--primary);
}
.btn-preset:active{
  transform:scale(0.95);
}
.info-note{
  margin:8px 0 0;
  font-size:13px;
  color:var(--muted);
  line-height:1.6;
}
.info-note strong{
  color:#f59e0b;
}
.example-text{
  font-size:12px;
  color:var(--primary);
  font-style:italic;
  margin:4px 0 8px;
}

.draggable-wrap{margin:10px 0}
.drag-help{color:var(--muted); font-size:12px; margin-bottom:6px}
.drag-list{display:flex; gap:8px; list-style:none; padding:0; margin:0}
.drag-list li{
  border:1px dashed var(--primary);
  background:#fff;
  color:#0369a1;
  padding:8px 12px;
  border-radius:10px;
  cursor:grab;
  user-select:none;
  transition: all 0.15s ease;
}
.drag-list li:hover{
  background:var(--primary-ghost);
  border-color:#0284c7;
}
.drag-list li:active{
  cursor:grabbing;
  opacity:0.6;
  transform:scale(1.05);
}
.drag-list li.dragging{
  opacity:0.4;
  border-style:solid;
}

footer{margin:20px 0; text-align:center}
.footer{
  display:inline-block;
  background:#fff;
  border:1px solid var(--border);
  padding:8px 14px;
  border-radius:999px;
  color:var(--muted);
}

.toast{
  position: fixed;
  left: 50%;
  transform: translateX(-50%);
  bottom: 24px;
  background: #111827;
  color: #fff;
  padding: 10px 14px;
  border-radius: 10px;
  opacity: 0;
  pointer-events: none;
  transition: opacity .2s ease, transform .2s ease;
}
.toast.show{
  opacity: 1;
  transform: translateX(-50%) translateY(-4px);
}
.toast.success{background: var(--accent)}
.toast.danger{background: var(--danger)}