/* ==========================================================================
   CSS Custom Properties / Design Tokens
   ========================================================================== */
:root {
  --color-primary: #4f46e5;
  --color-primary-hover: #4338ca;
  --color-primary-active: #3730a3;
  --color-primary-light: #eef2ff;
  --color-primary-focus: rgba(79, 70, 229, 0.25);
  --color-bg-base: #f8fafc;
  --color-bg-card: #ffffff;
  --color-bg-subtle: #f1f5f9;
  --color-bg-hover: #e2e8f0;
  --color-text-main: #0f172a;
  --color-text-muted: #64748b;
  --color-text-subtle: #94a3b8;
  --color-text-inverse: #ffffff;
  --color-border: #e2e8f0;
  --color-border-hover: #cbd5e1;
  --color-border-focus: #4f46e5;
  --color-error: #ef4444;
  --color-error-bg: #fef2f2;
  --color-error-border: #fecaca;
  --color-success: #10b981;
  --color-success-bg: #ecfdf5;
  
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 0.75rem;
  --spacing-lg: 1rem;
  --spacing-xl: 1.5rem;
  
  --radius-sm: 0.375rem;
  --radius-md: 0.625rem;
  --radius-lg: 0.875rem;
  --radius-xl: 1.25rem;
  --radius-full: 9999px;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.08), 0 8px 10px -6px rgba(15, 23, 42, 0.04);
  
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --min-touch-target: 48px;
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  height: 100%;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.5;
  color: var(--color-text-main);
  background-color: var(--color-bg-base);
  background-image:
    radial-gradient(at 0% 0%, rgba(79, 70, 229, 0.06) 0px, transparent 50%),
    radial-gradient(at 100% 100%, rgba(99, 102, 241, 0.05) 0px, transparent 50%);
  background-attachment: fixed;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: var(--spacing-lg);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Card Container */
.app-card {
  background-color: var(--color-bg-card);
  width: 100%;
  max-width: 440px;
  border-radius: var(--radius-xl);
  padding: clamp(1.25rem, 5vw, 2rem);
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--color-border);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

/* Header */
.app-header {
  text-align: center;
}

.brand-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto var(--spacing-sm);
  background-color: var(--color-primary-light);
  color: var(--color-primary);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-sm);
}

.brand-icon svg {
  width: 26px;
  height: 26px;
}

.app-title {
  font-size: clamp(1.35rem, 4vw, 1.625rem);
  font-weight: 700;
  color: var(--color-text-main);
  letter-spacing: -0.025em;
  margin-bottom: var(--spacing-xs);
}

.app-subtitle {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  line-height: 1.4;
}

/* Form & Inputs */
.qr-form {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  width: 100%;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
  position: relative;
}

.form-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-main);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
}

.input-icon-left {
  position: absolute;
  left: 0.875rem;
  color: var(--color-text-subtle);
  pointer-events: none;
  display: flex;
  align-items: center;
  justify-content: center;
}

.input-icon-left svg {
  width: 18px;
  height: 18px;
}

.text-input {
  width: 100%;
  min-height: var(--min-touch-target);
  font-family: inherit;
  font-size: var(--font-size-base);
  color: var(--color-text-main);
  background-color: var(--color-bg-base);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 0.75rem 2.5rem 0.75rem 2.625rem;
  transition: border-color var(--transition-fast), background-color var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
  -webkit-appearance: none;
  appearance: none;
}

.text-input::placeholder {
  color: var(--color-text-subtle);
  font-size: var(--font-size-sm);
}

.text-input:hover {
  border-color: var(--color-border-hover);
}

.text-input:focus {
  border-color: var(--color-border-focus);
  background-color: var(--color-bg-card);
  box-shadow: 0 0 0 3px var(--color-primary-focus);
}

.text-input.input-error {
  border-color: var(--color-error);
  background-color: var(--color-error-bg);
  animation: shake 0.3s cubic-bezier(0.36, 0.07, 0.19, 0.97) both;
}

.clear-btn {
  position: absolute;
  right: 0.5rem;
  background: none;
  border: none;
  padding: 0.5rem;
  color: var(--color-text-subtle);
  border-radius: var(--radius-full);
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  min-height: 36px;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.clear-btn:hover {
  color: var(--color-text-main);
  background-color: var(--color-bg-hover);
}

.clear-btn.visible {
  display: flex;
}

.error-msg {
  font-size: var(--font-size-xs);
  color: var(--color-error);
  font-weight: 500;
  min-height: 1.125rem;
  display: flex;
  align-items: center;
  gap: 0.375rem;
  opacity: 0;
  transform: translateY(-4px);
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}

.error-msg.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Buttons */
.btn {
  min-height: var(--min-touch-target);
  padding: 0.75rem 1.25rem;
  font-family: inherit;
  font-size: var(--font-size-base);
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  text-decoration: none;
  transition: all var(--transition-fast);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  position: relative;
  touch-action: manipulation;
}

.btn:active {
  transform: scale(0.98);
}

.btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.btn-primary {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
  box-shadow: 0 1px 2px 0 rgba(79, 70, 229, 0.2);
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  box-shadow: 0 4px 8px 0 rgba(79, 70, 229, 0.25);
}

.btn-secondary {
  background-color: var(--color-bg-card);
  color: var(--color-text-main);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:hover {
  background-color: var(--color-bg-subtle);
  border-color: var(--color-border-hover);
  color: var(--color-primary);
}

.btn-generate {
  width: 100%;
}

/* QR Display Section */
.qr-preview-section {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-lg);
  padding-top: var(--spacing-sm);
  opacity: 0;
  max-height: 0;
  overflow: hidden;
  transition: opacity var(--transition-normal), max-height 400ms ease, padding var(--transition-normal);
  pointer-events: none;
}

.qr-preview-section.active {
  opacity: 1;
  max-height: 800px;
  pointer-events: auto;
}

.qr-frame {
  background-color: var(--color-bg-base);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: clamp(1rem, 4vw, 1.25rem);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 100%;
  box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, 0.02);
}

.qr-canvas-container {
  background-color: #ffffff;
  padding: 12px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  border: 1px solid rgba(0, 0, 0, 0.04);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  max-width: 260px;
  aspect-ratio: 1 / 1;
}

#qr-code {
  display: block;
  width: 100% !important;
  height: 100% !important;
  object-fit: contain;
  border-radius: var(--radius-sm);
}

.qr-caption {
  margin-top: var(--spacing-sm);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  text-align: center;
  word-break: break-all;
  max-width: 90%;
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.action-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--spacing-sm);
  width: 100%;
}

.action-grid .btn-full {
  grid-column: span 2;
}

/* Toast Notification */
.toast-container {
  position: fixed;
  bottom: 1.5rem;
  left: 50%;
  transform: translateX(-50%) translateY(100px);
  background-color: var(--color-text-main);
  color: var(--color-text-inverse);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  opacity: 0;
  transition: transform var(--transition-normal), opacity var(--transition-normal);
  z-index: 1000;
  pointer-events: none;
  max-width: calc(100% - 2rem);
  white-space: nowrap;
}

.toast-container.toast-visible {
  transform: translateX(-50%) translateY(0);
  opacity: 1;
}

.toast-icon {
  display: flex;
  align-items: center;
  color: var(--color-success);
}

.toast-icon svg {
  width: 18px;
  height: 18px;
}

/* Animations */
@keyframes shake {
  10%, 90% { transform: translate3d(-1px, 0, 0); }
  20%, 80% { transform: translate3d(2px, 0, 0); }
  30%, 50%, 70% { transform: translate3d(-3px, 0, 0); }
  40%, 60% { transform: translate3d(3px, 0, 0); }
}

@keyframes fadeInScale {
  from { opacity: 0; transform: scale(0.95); }
  to { opacity: 1; transform: scale(1); }
}

.animate-pop {
  animation: fadeInScale 0.3s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

/* Responsive */
@media (max-width: 480px) {
  body { padding: 0.75rem; }
  .app-card { padding: 1.25rem 1rem; gap: var(--spacing-md); border-radius: var(--radius-lg); }
  .action-grid { grid-template-columns: 1fr; }
  .action-grid .btn-full { grid-column: span 1; }
  .btn { width: 100%; font-size: var(--font-size-sm); }
}