/* ==========================================================================
   SiliconSignature PWA Stylesheet
   Professional dark theme with amber/gold accents
   Mobile-first responsive design
   ========================================================================== */

/* --------------------------------------------------------------------------
   CSS Variables / Design Tokens
   -------------------------------------------------------------------------- */
:root {
  /* Colors */
  --bg-primary: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-tertiary: #0f3460;
  --bg-card: #1e1e3a;
  --bg-hover: #252550;
  --bg-input: #131335;

  --accent: #f5a623;
  --accent-light: #ffc84a;
  --accent-dark: #d68a1a;
  --accent-glow: rgba(245, 166, 35, 0.15);

  --text-primary: #eaeaea;
  --text-secondary: #a0a0b8;
  --text-muted: #6a6a82;

  --success: #4ade80;
  --success-bg: rgba(74, 222, 128, 0.1);
  --error: #f87171;
  --error-bg: rgba(248, 113, 113, 0.1);
  --warning: #fbbf24;
  --warning-bg: rgba(251, 191, 36, 0.1);

  /* Borders */
  --border-color: rgba(255, 255, 255, 0.06);
  --border-accent: rgba(245, 166, 35, 0.3);

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);
  --shadow-accent: 0 0 20px rgba(245, 166, 35, 0.1);

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

  /* Radii */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;

  /* Typography */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

/* --------------------------------------------------------------------------
   Reset & Base
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

img {
  max-width: 100%;
  height: auto;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
}

input {
  font-family: inherit;
}

/* --------------------------------------------------------------------------
   Scrollbar
   -------------------------------------------------------------------------- */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg-primary);
}
::-webkit-scrollbar-thumb {
  background: var(--bg-tertiary);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-dark);
}

/* --------------------------------------------------------------------------
   App Header
   -------------------------------------------------------------------------- */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(26, 26, 46, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  color: inherit;
}

.logo-icon {
  width: 36px;
  height: 36px;
  flex-shrink: 0;
}

.logo-icon svg {
  width: 100%;
  height: 100%;
}

.logo-text {
  display: flex;
  align-items: baseline;
  gap: var(--space-xs);
}

.logo-title {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.3px;
  color: var(--text-primary);
}

.logo-subtitle {
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--accent);
  background: var(--accent-glow);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid var(--border-accent);
}

/* Main Nav */
.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-hover);
}

.nav-link.active {
  color: var(--accent);
  background: var(--accent-glow);
}

.nav-icon {
  width: 18px;
  height: 18px;
}

/* --------------------------------------------------------------------------
   App Main
   -------------------------------------------------------------------------- */
.app-main {
  max-width: 900px;
  margin: 0 auto;
  padding: var(--space-xl) var(--space-lg);
  min-height: calc(100vh - 64px - 60px);
}

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */
.hero {
  text-align: center;
  margin-bottom: var(--space-2xl);
  padding: var(--space-xl) 0;
}

.hero-title {
  font-size: clamp(1.6rem, 4vw, 2.4rem);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--space-md);
  letter-spacing: -0.5px;
}

.hero-accent {
  color: var(--accent);
}

.hero-desc {
  font-size: clamp(0.9rem, 2vw, 1.05rem);
  color: var(--text-secondary);
  max-width: 580px;
  margin: 0 auto;
  line-height: 1.7;
}

/* --------------------------------------------------------------------------
   Section Common
   -------------------------------------------------------------------------- */
.section {
  animation: fadeIn var(--transition-slow);
}

.section.hidden {
  display: none;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.section-title {
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.section-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

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

/* --------------------------------------------------------------------------
   Creator Input
   -------------------------------------------------------------------------- */
.creator-input-wrap {
  margin-bottom: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.creator-label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.creator-input {
  width: 100%;
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.95rem;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.creator-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.creator-input::placeholder {
  color: var(--text-muted);
}

/* --------------------------------------------------------------------------
   Drop Zone
   -------------------------------------------------------------------------- */
.drop-zone {
  position: relative;
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-lg);
  background: var(--bg-card);
  transition: all var(--transition-base);
  overflow: hidden;
  min-height: 320px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.drop-zone:hover {
  border-color: var(--border-accent);
  box-shadow: var(--shadow-accent);
}

.drop-zone.drag-over {
  border-color: var(--accent);
  background: var(--accent-glow);
  box-shadow: var(--shadow-accent);
}

.drop-zone-inner {
  width: 100%;
  padding: var(--space-xl);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.drop-zone-inner.has-image {
  padding: 0;
}

.drop-zone-inner.has-image .drop-placeholder {
  display: none;
}

.file-input {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
  z-index: 2;
}

/* Drop Placeholder */
.drop-placeholder {
  text-align: center;
  pointer-events: none;
  user-select: none;
}

.drop-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto var(--space-md);
  opacity: 0.7;
}

.drop-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
}

.drop-subtitle {
  font-size: 0.9rem;
  color: var(--accent);
  margin-bottom: var(--space-sm);
}

.drop-hint {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Canvas Container */
.canvas-container {
  position: relative;
  width: 100%;
  max-height: 500px;
  overflow: auto;
  display: flex;
  justify-content: center;
  border-radius: var(--radius-md);
}

.main-canvas {
  max-width: 100%;
  max-height: 500px;
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
}

.main-canvas.hidden {
  display: none;
}

.heatmap-canvas {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  max-width: 100%;
  max-height: 500px;
  pointer-events: none;
  border-radius: var(--radius-sm);
}

.heatmap-canvas.hidden {
  display: none;
}

/* Image Info */
.image-info {
  margin-top: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  color: var(--text-muted);
  text-align: center;
  border: 1px solid var(--border-color);
}

.image-info.hidden {
  display: none;
}

/* --------------------------------------------------------------------------
   Action Panel
   -------------------------------------------------------------------------- */
.action-panel {
  margin-top: var(--space-lg);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
}

.action-panel.hidden {
  display: none;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  font-weight: 600;
  transition: all var(--transition-fast);
  min-height: 42px;
  position: relative;
  z-index: 3;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-icon {
  width: 18px;
  height: 18px;
}

.btn-primary {
  background: var(--accent);
  color: var(--bg-primary);
  box-shadow: 0 2px 8px rgba(245, 166, 35, 0.3);
}

.btn-primary:hover:not(:disabled) {
  background: var(--accent-light);
  box-shadow: 0 4px 16px rgba(245, 166, 35, 0.4);
  transform: translateY(-1px);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--bg-hover);
  border-color: var(--border-accent);
}

.btn-accent {
  background: var(--success);
  color: #0a1f0a;
  box-shadow: 0 2px 8px rgba(74, 222, 128, 0.25);
}

.btn-accent:hover:not(:disabled) {
  background: #6ee89a;
  box-shadow: 0 4px 16px rgba(74, 222, 128, 0.35);
  transform: translateY(-1px);
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

.btn-ghost:hover:not(:disabled) {
  color: var(--text-primary);
  border-color: var(--text-muted);
  background: var(--bg-hover);
}

.btn-ghost.active {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

.btn.hidden {
  display: none;
}

/* Processing state */
.btn.processing {
  animation: pulse-btn 1.5s infinite;
}

@keyframes pulse-btn {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.7; }
}

/* --------------------------------------------------------------------------
   Progress Panel
   -------------------------------------------------------------------------- */
.progress-panel {
  margin-top: var(--space-lg);
  padding: var(--space-lg);
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
}

.progress-panel.hidden {
  display: none;
}

.progress-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-sm);
}

.progress-stage {
  font-weight: 600;
  font-size: 0.95rem;
}

.progress-percent {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent);
  font-weight: 500;
}

.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--bg-primary);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: var(--space-sm);
}

.progress-bar-fill {
  height: 100%;
  width: 0%;
  background: var(--accent);
  border-radius: 4px;
  transition: width 0.3s ease;
  box-shadow: 0 0 10px rgba(245, 166, 35, 0.3);
}

.progress-detail {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: var(--space-sm);
  min-height: 1.2em;
  font-family: var(--font-mono);
}

.progress-stats {
  display: flex;
  gap: var(--space-lg);
  padding-top: var(--space-sm);
  border-top: 1px solid var(--border-color);
}

.stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.stat-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
}

.stat-value {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-secondary);
}

/* --------------------------------------------------------------------------
   Result Panel
   -------------------------------------------------------------------------- */
.result-panel {
  margin-top: var(--space-lg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border-color);
  animation: slideUp var(--transition-slow);
}

.result-panel.hidden {
  display: none;
}

.result-panel.success {
  border-color: rgba(74, 222, 128, 0.3);
}

.result-panel.error {
  border-color: rgba(248, 113, 113, 0.3);
}

.result-panel.warning {
  border-color: rgba(251, 191, 36, 0.3);
}

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

.result-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-lg);
}

.result-panel.success .result-header {
  background: var(--success-bg);
}

.result-panel.error .result-header {
  background: var(--error-bg);
}

.result-panel.warning .result-header {
  background: var(--warning-bg);
}

.result-indicator {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  flex-shrink: 0;
}

.result-panel.success .result-indicator {
  background: var(--success);
  box-shadow: 0 0 8px rgba(74, 222, 128, 0.4);
}

.result-panel.error .result-indicator {
  background: var(--error);
  box-shadow: 0 0 8px rgba(248, 113, 113, 0.4);
}

.result-panel.warning .result-indicator {
  background: var(--warning);
  box-shadow: 0 0 8px rgba(251, 191, 36, 0.4);
}

.result-status {
  font-size: 1.1rem;
  font-weight: 600;
}

.result-panel.success .result-status {
  color: var(--success);
}

.result-panel.error .result-status {
  color: var(--error);
}

.result-panel.warning .result-status {
  color: var(--warning);
}

.result-content {
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-card);
}

/* Result detail rows */
.result-detail {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.detail-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border-color);
  gap: var(--space-md);
}

.detail-row:last-child {
  border-bottom: none;
}

.detail-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  flex-shrink: 0;
  min-width: 120px;
}

.detail-value {
  font-size: 0.85rem;
  font-weight: 500;
  text-align: right;
  word-break: break-all;
}

.detail-value.mono {
  font-family: var(--font-mono);
  font-size: 0.75rem;
}

.status-badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.status-badge.success {
  background: var(--success-bg);
  color: var(--success);
  border: 1px solid rgba(74, 222, 128, 0.2);
}

.status-badge.error {
  background: var(--error-bg);
  color: var(--error);
  border: 1px solid rgba(248, 113, 113, 0.2);
}

.status-badge.warning {
  background: var(--warning-bg);
  color: var(--warning);
  border: 1px solid rgba(251, 191, 36, 0.2);
}

.error-message {
  color: var(--error);
  margin-bottom: var(--space-sm);
}

.verify-note {
  margin-top: var(--space-md);
  padding-top: var(--space-md);
  border-top: 1px solid var(--border-color);
  font-size: 0.85rem;
  color: var(--text-secondary);
}

/* --------------------------------------------------------------------------
   Signature Details
   -------------------------------------------------------------------------- */
.sig-details {
  margin-top: var(--space-lg);
  padding: var(--space-lg);
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  animation: slideUp var(--transition-slow);
}

.sig-details.hidden {
  display: none;
}

.sig-title {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: var(--space-md);
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-size: 0.75rem;
}

.sig-grid {
  display: grid;
  gap: var(--space-sm);
}

.sig-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border-color);
  gap: var(--space-md);
}

.sig-item:last-child {
  border-bottom: none;
}

.sig-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  flex-shrink: 0;
  min-width: 100px;
}

.sig-value {
  font-size: 0.8rem;
  font-weight: 500;
  text-align: right;
  word-break: break-all;
  font-family: var(--font-mono);
}

/* --------------------------------------------------------------------------
   History
   -------------------------------------------------------------------------- */
.history-panel {
  margin-top: var(--space-lg);
}

.history-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.history-empty {
  text-align: center;
  padding: var(--space-2xl);
  color: var(--text-muted);
}

.empty-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto var(--space-md);
  border-radius: 50%;
  background: var(--bg-card);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-muted);
  border: 1px solid var(--border-color);
}

.history-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.history-item:hover {
  border-color: var(--border-accent);
  background: var(--bg-hover);
  transform: translateX(4px);
}

.history-icon {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
  flex-shrink: 0;
}

.history-icon.sign {
  background: var(--accent-glow);
  color: var(--accent);
  border: 1px solid var(--border-accent);
}

.history-icon.verify {
  background: rgba(74, 222, 128, 0.1);
  color: var(--success);
  border: 1px solid rgba(74, 222, 128, 0.2);
}

.history-info {
  flex: 1;
  min-width: 0;
}

.history-filename {
  font-size: 0.85rem;
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  margin-bottom: 2px;
}

.history-meta {
  display: flex;
  gap: var(--space-sm);
  font-size: 0.75rem;
  color: var(--text-muted);
}

.history-type {
  text-transform: capitalize;
}

.history-status {
  font-size: 0.7rem;
  font-weight: 600;
  padding: 3px 8px;
  border-radius: 20px;
  flex-shrink: 0;
}

.history-status.success {
  background: var(--success-bg);
  color: var(--success);
}

.history-status.error {
  background: var(--error-bg);
  color: var(--error);
}

.history-status.warning {
  background: var(--warning-bg);
  color: var(--warning);
}

/* --------------------------------------------------------------------------
   About
   -------------------------------------------------------------------------- */
.about-container {
  max-width: 700px;
  margin: 0 auto;
}

.about-title {
  font-size: 1.6rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--space-xl);
}

.about-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.about-card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  color: var(--accent);
}

.about-card p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: var(--space-sm);
}

.about-card p:last-child {
  margin-bottom: 0;
}

.about-steps {
  list-style: none;
  counter-reset: step;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.about-steps li {
  position: relative;
  padding-left: 36px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.about-steps li::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0;
  width: 24px;
  height: 24px;
  background: var(--accent-glow);
  border: 1px solid var(--border-accent);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--accent);
}

.about-steps strong {
  color: var(--text-primary);
}

.spec-grid {
  display: grid;
  gap: var(--space-sm);
}

.spec-item {
  display: flex;
  justify-content: space-between;
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border-color);
  gap: var(--space-md);
}

.spec-item:last-child {
  border-bottom: none;
}

.spec-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  flex-shrink: 0;
}

.spec-value {
  font-size: 0.85rem;
  font-weight: 500;
  text-align: right;
  font-family: var(--font-mono);
}

.about-footer {
  text-align: center;
  padding: var(--space-lg) 0;
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* --------------------------------------------------------------------------
   Modal
   -------------------------------------------------------------------------- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.7);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: var(--space-lg);
  animation: fadeIn 200ms;
}

.modal-overlay.hidden {
  display: none;
}

.modal-dialog {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  max-width: 520px;
  width: 100%;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
  animation: slideUp 300ms;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-md) var(--space-lg);
  border-bottom: 1px solid var(--border-color);
}

.modal-title {
  font-size: 1.05rem;
  font-weight: 600;
}

.modal-close {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  font-size: 1.4rem;
  color: var(--text-muted);
  transition: all var(--transition-fast);
  line-height: 1;
}

.modal-close:hover {
  color: var(--text-primary);
  background: var(--bg-hover);
}

.modal-body {
  padding: var(--space-lg);
}

.modal-sig-details .detail-row {
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border-color);
  gap: var(--space-md);
}

.modal-sig-details .detail-row:last-child {
  border-bottom: none;
}

.modal-sig-details .detail-label {
  min-width: 100px;
}

.modal-sig-details hr {
  border: none;
  border-top: 1px solid var(--border-color);
  margin: var(--space-sm) 0;
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */
.app-footer {
  text-align: center;
  padding: var(--space-lg);
  border-top: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* --------------------------------------------------------------------------
   Responsive (Mobile-First)
   -------------------------------------------------------------------------- */
@media (max-width: 640px) {
  .header-inner {
    padding: 0 var(--space-md);
    height: 56px;
  }

  .logo-title {
    font-size: 1rem;
  }

  .logo-subtitle {
    display: none;
  }

  .main-nav {
    gap: 0;
  }

  .nav-link {
    padding: var(--space-sm);
  }

  .nav-link span {
    display: none;
  }

  .nav-icon {
    width: 20px;
    height: 20px;
  }

  .app-main {
    padding: var(--space-md);
  }

  .hero {
    margin-bottom: var(--space-lg);
    padding: var(--space-md) 0;
  }

  .drop-zone {
    min-height: 240px;
  }

  .drop-zone-inner {
    padding: var(--space-lg);
  }

  .drop-title {
    font-size: 1rem;
  }

  .action-panel {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }

  .progress-stats {
    flex-direction: column;
    gap: var(--space-sm);
  }

  .detail-row {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-xs);
  }

  .sig-item {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-xs);
  }

  .sig-value {
    text-align: left;
  }

  .history-item {
    padding: var(--space-sm);
  }

  .history-meta {
    flex-direction: column;
    gap: 2px;
  }

  .about-steps li {
    padding-left: 32px;
    font-size: 0.85rem;
  }
}

@media (min-width: 768px) {
  .drop-zone {
    min-height: 400px;
  }
}