:root {
  /* Light Mode Color Palette */
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-accent: #e0f2fe;
  --border: #e2e8f0;
  --border-hover: #3b82f6;

  /* Text Colors */
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;

  /* Accent Colors */
  --accent-blue: #3b82f6;
  --accent-blue-hover: #2563eb;
  --accent-green: #10b981;
  --accent-yellow: #f59e0b;
  --accent-red: #ef4444;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);

  /* Highlight Colors for Cipher Visualization */
  --highlight-plain: #fef3c7;
  --highlight-active: #bfdbfe;
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
  margin: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", "Hiragino Sans", "Noto Sans JP", Arial, sans-serif;
  color: var(--text-primary);
  background: linear-gradient(135deg, #f5f7fa 0%, #f0f4f8 100%);
  line-height: 1.6;
}

/* Header */
header {
  max-width: 1200px;
  margin: 0 auto;
  padding: 32px 20px 20px;
  background: transparent;
}

h1 {
  margin: 0 0 8px;
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, var(--accent-blue) 0%, #1e40af 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  margin: 0;
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
}

/* Tabs Navigation */
.tabs {
  max-width: 1200px;
  margin: 0 auto 24px;
  display: flex;
  gap: 6px;
  padding: 0 20px;
  overflow-x: auto;
  scrollbar-width: thin;
}

.tab-btn {
  appearance: none;
  border: 2px solid transparent;
  background: var(--bg-secondary);
  color: var(--text-secondary);
  padding: 8px 16px;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 500;
  font-size: 13px;
  white-space: nowrap;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.tab-btn:hover {
  background: var(--bg-accent);
  color: var(--accent-blue);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.tab-btn.active {
  background: var(--accent-blue);
  color: white;
  box-shadow: var(--shadow-md);
}

/* Main Content Area */
main {
  padding: 0 20px 40px;
  max-width: 1200px;
  margin: 0 auto;
}

.tab-panel {
  display: none;
  animation: fadeIn 0.3s ease;
}

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

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Grid Layout */
.panel-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

@media (max-width: 960px) {
  .panel-grid {
    grid-template-columns: 1fr;
  }
}

/* Encryption Layout */
.enc-simple-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  margin-bottom: 24px;
}

.enc-strips {
  margin-top: 0;
}

.enc-strips-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
}

.cipher-line-controls-header {
  display: flex;
  align-items: center;
  gap: 8px;
}

.cipher-offset-label {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
}

.enc-strips-container {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: flex-start;
  padding: 16px;
  padding-left: 180px; /* ラベル分のスペースを確保 */
  background: var(--bg-accent);
  border-radius: 8px;
  position: relative;
  overflow: visible; /* 上方向へのはみ出しを許容して無駄な余白を避ける */
}

/* 復号タブでは枠からのはみ出しを抑制 */
#decStripsDisplay.enc-strips-container {
  overflow: hidden;
}

/* 基準線（平文） */
/* 基準線（平文）- JavaScriptで動的生成するため無効化 */
.enc-strips-container::before {
  display: none;
}

.enc-strips-container::after {
  display: none;
}

/* 暗号文ライン */
.cipher-line {
  position: absolute;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--accent-blue);
  z-index: 10;
  pointer-events: none;
  box-shadow: 0 0 4px rgba(59, 130, 246, 0.5);
  cursor: ns-resize;
}

.cipher-line-label {
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  background: var(--accent-blue);
  color: white;
  padding: 4px 8px;
  border-radius: 4px;
  font-size: 12px;
  font-weight: bold;
  z-index: 11;
  pointer-events: none;
  white-space: nowrap;
}


.cipher-control-btn {
  background: var(--accent-blue);
  color: white;
  border: none;
  width: 24px;
  height: 24px;
  border-radius: 4px;
  cursor: pointer;
  font-size: 14px;
  font-weight: bold;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.2s;
}

.cipher-control-btn:hover:not(:disabled) {
  background: var(--accent-blue-hover);
}

.cipher-control-btn:disabled {
  background: var(--text-muted);
  cursor: not-allowed;
}

@media (max-width: 960px) {
  .enc-simple-layout {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .enc-strips-container {
    gap: 12px;
  }
}

/* Read-only encryption strips */
.enc-strip-readonly {
  pointer-events: none;
}

/* Ensure consistent character height for position calculations */
.actual-strip-char {
  height: 24px !important;
  line-height: 24px !important;
}

/* Normalize rows in encryption view to avoid vertical jitter */
.enc-strips-container .actual-strip-body {
  padding: 0 !important;
}

.enc-strips-container .actual-strip-char {
  margin: 0 !important;
  border: 0 !important;
}

/* Highlight styles for active characters */
.actual-strip-char.highlight-active {
  background: var(--accent-yellow) !important;
  color: var(--text-primary);
  font-weight: bold;
  border: 2px solid var(--accent-red);
  box-shadow: 0 0 8px rgba(239, 68, 68, 0.3);
}



/* Warning messages */
.warnings {
  margin-top: 8px;
  font-size: 14px;
}

.warning-message {
  background: var(--accent-yellow);
  color: var(--text-primary);
  padding: 6px 12px;
  border-radius: 4px;
  margin-bottom: 4px;
  border-left: 4px solid var(--accent-red);
  font-weight: 500;
}

.warning-message:last-child {
  margin-bottom: 0;
}

/* Textarea with copy button */
.textarea-container {
  position: relative;
}

.copy-button {
  position: absolute;
  top: -8px;
  right: -8px;
  background: var(--accent-blue);
  color: white;
  border: none;
  padding: 6px 10px;
  border-radius: 6px;
  font-size: 12px;
  cursor: pointer;
  z-index: 10;
  transition: background-color 0.2s;
  box-shadow: var(--shadow-md);
  border: 2px solid white;
}

.copy-button:hover {
  background: var(--accent-blue-hover);
}

.copy-button:active {
  transform: translateY(1px);
}

/* Cipher output header (button outside the textarea) */
.cipher-output-card .cipher-output-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px; /* match .card h2 default spacing */
}

.header-actions {
  display: flex;
  gap: 8px;
}

/* Decrypt input header matches output header spacing */
.cipher-input-card .cipher-input-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.cipher-input-card .cipher-input-header h2 {
  margin: 0;
}

.cipher-input-card .cipher-input-header .copy-button {
  position: static;
  top: auto;
  right: auto;
  border: none;
}

/* Plaintext input header (encrypt tab) */
.plain-input-card .plain-input-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.plain-input-card .plain-input-header h2 {
  margin: 0;
}

.plain-input-card .plain-input-header .copy-button {
  position: static;
  top: auto;
  right: auto;
  border: none;
}

.cipher-output-card .cipher-output-header h2 {
  margin: 0;
}

.cipher-output-card .cipher-output-header .copy-button {
  position: static;
  top: auto;
  right: auto;
  border: none;
}

/* Toast notification */
.toast {
  position: fixed;
  top: 20px;
  right: 20px;
  background: var(--accent-green);
  color: white;
  padding: 12px 16px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  z-index: 1000;
  opacity: 0;
  transform: translateX(100px);
  transition: all 0.3s ease;
}

.toast.show {
  opacity: 1;
  transform: translateX(0);
}

/* Card Design */
.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 24px;
  box-shadow: var(--shadow-md);
  transition: box-shadow 0.2s ease;
}

.card:hover {
  box-shadow: var(--shadow-lg);
}

.card h2 {
  margin: 0 0 20px;
  font-size: 18px;
  font-weight: 600;
  color: var(--text-primary);
}

/* Form Elements */
.row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 12px 0;
  flex-wrap: wrap;
}

.row label {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-secondary);
  min-width: fit-content;
}

input[type="text"],
input[type="number"],
select,
textarea {
  background: var(--bg-primary);
  color: var(--text-primary);
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 8px 12px;
  outline: none;
  width: 100%;
  font-size: 13px;
  transition: all 0.2s ease;
}

input[type="number"] {
  max-width: 100px;
}

input[type="text"]:focus,
input[type="number"]:focus,
select:focus,
textarea:focus {
  border-color: var(--accent-blue);
  background: white;
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

textarea {
  resize: vertical;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  line-height: 1.5;
}

/* Buttons */
button {
  background: white;
  color: var(--text-primary);
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 8px 16px;
  cursor: pointer;
  font-weight: 500;
  font-size: 13px;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
  min-width: fit-content;
  white-space: nowrap;
}

button:hover {
  background: var(--bg-primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-blue);
}

button.primary {
  background: var(--accent-blue);
  color: white;
  border-color: transparent;
}

button.primary:hover {
  background: var(--accent-blue-hover);
  box-shadow: var(--shadow-lg);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Utility Classes */
.mono {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Courier New", monospace;
}

.small {
  font-size: 12px;
}

.dim {
  color: var(--text-muted);
}

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

.btn-row label {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-secondary);
  margin-right: 4px;
}

.btn-row input[type="number"] {
  max-width: 80px;
  flex: 0 0 auto;
}

.note {
  background: var(--bg-accent);
  border-left: 4px solid var(--accent-blue);
  padding: 12px 16px;
  margin: 16px 0;
  border-radius: 8px;
  font-size: 14px;
  color: var(--text-secondary);
}

/* Strip Visualization */
.strips-container {
  display: flex;
  gap: 16px;
  padding: 20px;
  background: var(--bg-primary);
  border-radius: 12px;
  overflow-x: auto;
  min-height: 400px;
}

.strip {
  flex: 0 0 auto;
  width: 80px;
  background: white;
  border: 2px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  position: relative;
  transition: transform 0.2s ease;
}

.strip:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.strip-header {
  background: var(--accent-blue);
  color: white;
  padding: 8px;
  text-align: center;
  font-weight: 600;
  font-size: 14px;
  border-radius: 6px 6px 0 0;
}

.strip-body {
  flex: 1;
  position: relative;
  height: 520px;
  overflow-y: auto;
  overflow-x: hidden;
  background: var(--bg-primary);
  padding: 4px;
}

.strip-letters {
  width: 100%;
}

.strip-char {
  height: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  border-bottom: 1px solid rgba(226, 232, 240, 0.3);
}

.strip-position {
  padding: 6px;
  text-align: center;
  font-size: 11px;
  color: var(--text-muted);
  background: var(--bg-primary);
  border-radius: 0 0 6px 6px;
}

/* Frame Layout */
.frame-layout {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.advanced-settings {
  order: 1;
}

.main-strips {
  order: 2;
  flex: 1;
}

/* Collapsible Content */
.collapsible-header {
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
  transition: background 0.2s ease;
  margin: 0 0 12px;
  padding: 8px 0;
}

.collapsible-header:hover {
  color: var(--accent-blue);
}

.toggle-icon {
  font-size: 12px;
  transition: transform 0.2s ease;
}

.collapsible-content {
  transition: max-height 0.3s ease, opacity 0.2s ease;
  overflow: hidden;
}

.collapsible-content.collapsed {
  max-height: 0;
  opacity: 0;
}

.collapsible-content:not(.collapsed) {
  max-height: 500px;
  opacity: 1;
}

.hint {
  font-size: 13px;
  color: var(--text-muted);
  margin: 0 0 16px;
  font-style: italic;
}

/* Drag and Drop */
.draggable-strip[draggable="true"] {
  cursor: grab;
}

.draggable-strip[draggable="true"]:active {
  cursor: grabbing;
}

.draggable-strip.dragging {
  opacity: 0.5;
  transform: rotate(2deg);
}

.draggable-strip.drop-target {
  border-color: var(--accent-blue);
  border-width: 3px;
  background: var(--bg-accent);
  transform: scale(1.02);
  box-shadow: 0 0 15px rgba(59, 130, 246, 0.3);
}

/* Build Tab Layout */
.build-layout {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* Top row for generation and editing */
.build-top-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

@media (max-width: 960px) {
  .build-top-row {
    grid-template-columns: 1fr;
  }
}

.generation-settings {
  order: 1;
}

.alphabet-editing {
  order: 2;
}

.actual-strips {
  order: 3;
}

/* Actual Strips Display */
.actual-strips-container {
  display: flex;
  gap: 12px;
  padding: 16px;
  background: var(--bg-primary);
  border-radius: 12px;
  overflow-x: auto;
  min-height: 200px;
  align-items: flex-start;
}

.no-strips-message {
  color: var(--text-muted);
  font-style: italic;
  text-align: center;
  width: 100%;
  padding: 40px 20px;
}

.actual-strip {
  flex: 0 0 auto;
  width: 60px;
  background: white;
  border: 2px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow-md);
  display: flex;
  flex-direction: column;
  min-height: 600px;
  transition: transform 0.2s ease;
}

.actual-strip:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.actual-strip-header {
  background: var(--accent-green);
  color: white;
  padding: 6px 4px;
  text-align: center;
  font-weight: 600;
  font-size: 12px;
  border-radius: 6px 6px 0 0;
  writing-mode: horizontal-tb;
}

.actual-strip-body {
  flex: 1;
  display: flex;
  flex-direction: column;
  background: linear-gradient(to bottom, #f8fafc 0%, #e2e8f0 100%);
  padding: 2px 0;
}

.actual-strip-char {
  height: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-primary);
  border-bottom: 1px solid rgba(226, 232, 240, 0.5);
  margin: 0 2px 1px;
  border-radius: 2px;
}

.actual-strip-char.first-section {
  background: white;
  border-left: 3px solid var(--accent-blue);
}

.actual-strip-char.repeat-section {
  background: var(--bg-accent);
  border-left: 3px solid var(--accent-yellow);
  color: var(--text-secondary);
}

.actual-strip-char.section-end {
  border-bottom: 3px solid var(--accent-red);
  margin-bottom: 3px;
}

/* Cipher Visualization */
.rows {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-top: 16px;
  padding: 16px;
  background: var(--bg-primary);
  border-radius: 12px;
}

.row-line {
  display: flex;
  gap: 12px;
  align-items: center;
  padding: 8px;
  border-radius: 8px;
  transition: background 0.2s ease;
}

.row-line:hover {
  background: var(--bg-accent);
}

.row-line .label {
  width: 100px;
  text-align: right;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 500;
}

.row-line .letters {
  font-size: 16px;
  letter-spacing: 3px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  white-space: pre;
}

.letters span {
  padding: 4px 6px;
  border-radius: 6px;
  transition: all 0.2s ease;
}


/* Marks Legend */
.mark {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 4px;
  margin: 0 4px;
}

.mark.base {
  background: var(--accent-yellow);
}

.mark.target {
  background: var(--accent-blue);
}

.mark.row {
  background: var(--accent-green);
}

/* Validation Messages */
#validateMsg, #encLog, #decLog {
  padding: 8px 12px;
  margin-top: 8px;
  border-radius: 8px;
  font-size: 13px;
}

#validateMsg:not(:empty) {
  background: var(--bg-accent);
  border-left: 4px solid var(--accent-blue);
}

/* Footer */
.footer {
  padding: 24px 20px;
  text-align: center;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  margin-top: 32px;
}

/* Checkbox Styling */
input[type="checkbox"] {
  width: 18px;
  height: 18px;
  margin-right: 8px;
  cursor: pointer;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}