* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  /* Colors */
  --bg-primary: #0a0a0f;
  --bg-secondary: #13131a;
  --bg-tertiary: #1a1a24;
  --bg-card: #1e1e2e;
  --bg-card-hover: #252538;
  
  --text-primary: #ffffff;
  --text-secondary: #a0a0b8;
  --text-muted: #6b6b8c;
  
  --accent-primary: #6366f1;
  --accent-secondary: #8b5cf6;
  --accent-hover: #7c3aed;
  
  --success: #10b981;
  --error: #ef4444;
  --warning: #f59e0b;
  
  --border-color: #2a2a3e;
  --border-radius: 16px;
  --border-radius-sm: 12px;
  --border-radius-lg: 24px;
  
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
  
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 350ms ease;
  
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 32px rgba(99, 102, 241, 0.3);
}

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

body {
  font-family: var(--font-family);
  background: linear-gradient(135deg, #0a0a0f 0%, #13131a 50%, #0d0d14 100%);
  background-attachment: fixed;
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
  overflow-x: hidden;
}

.container {
  max-width: 480px;
  margin: 0 auto;
  padding: var(--spacing-md);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

@media (min-width: 768px) {
  .container {
    max-width: 640px;
    padding: var(--spacing-lg);
  }
}

@media (min-width: 1024px) {
  .container {
    max-width: 720px;
  }
}

.header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  padding-top: var(--spacing-lg);
}

.logo {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-sm);
}

.logo h1 {
  font-size: 2rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tagline {
  color: var(--text-secondary);
  font-size: 1rem;
  margin-top: var(--spacing-xs);
}

.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--border-radius-sm);
  transition: all var(--transition-fast);
  margin-bottom: var(--spacing-md);
}

.back-btn:hover {
  color: var(--text-primary);
  background: var(--bg-card);
}

.back-btn svg {
  stroke: currentColor;
}

.header h1 {
  font-size: 1.75rem;
  margin-top: var(--spacing-sm);
}

.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.action-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
}

@media (min-width: 640px) {
  .action-cards {
    grid-template-columns: repeat(2, 1fr);
  }
}

.card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  text-decoration: none;
  color: var(--text-primary);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  transition: all var(--transition-normal);
  overflow: hidden;
  cursor: pointer;
  min-height: 220px;
}

.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.card:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-primary);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.card:hover::before {
  opacity: 1;
}

.card:active {
  transform: translateY(-2px);
}

.card-icon {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--spacing-md);
  color: var(--accent-primary);
  transition: all var(--transition-normal);
}

.card:hover .card-icon {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.2), rgba(139, 92, 246, 0.2));
  transform: scale(1.1);
}

.card h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-xs);
  font-weight: 600;
}

.card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: var(--spacing-md);
}

.card-arrow {
  margin-top: auto;
  font-size: 1.5rem;
  color: var(--accent-primary);
  transition: transform var(--transition-normal);
}

.card:hover .card-arrow {
  transform: translateX(4px);
}

.features {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  flex-wrap: wrap;
  padding: var(--spacing-lg) 0;
}

.feature {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.feature-icon {
  font-size: 1.25rem;
}

.upload-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.drop-zone {
  position: relative;
  border: 2px dashed var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-xl);
  text-align: center;
  transition: all var(--transition-normal);
  cursor: pointer;
  min-height: 320px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.drop-zone:hover {
  border-color: var(--accent-primary);
  background: rgba(99, 102, 241, 0.05);
}

.drop-zone.drag-over {
  border-color: var(--accent-primary);
  background: rgba(99, 102, 241, 0.1);
  border-style: solid;
}

.drop-zone-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-md);
}

.upload-icon {
  color: var(--accent-primary);
  opacity: 0.8;
  margin-bottom: var(--spacing-sm);
}

.drop-zone h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.drop-zone p {
  color: var(--text-secondary);
  margin: var(--spacing-xs) 0;
}

.file-size-hint {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: var(--spacing-sm);
}

/* File Preview */
.file-preview {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-md);
  width: 100%;
}

.file-info {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  flex: 1;
}

.file-info svg {
  color: var(--accent-primary);
  flex-shrink: 0;
}

.file-details {
  flex: 1;
  text-align: left;
  overflow: hidden;
}

.file-name {
  font-weight: 600;
  font-size: 1rem;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  margin-bottom: 0.25rem;
}

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

/* Progress Bar */
.progress-container {
  position: relative;
  width: 100%;
  height: 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  margin-top: var(--spacing-md);
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));
  transition: width 0.3s ease;
  border-radius: 8px;
}

.progress-text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-primary);
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
  z-index: 1;
}

.receive-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-xl);
  text-align: center;
}

.receive-icon {
  width: 96px;
  height: 96px;
  margin: 0 auto var(--spacing-lg);
  border-radius: 50%;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent-primary);
}

.receive-card h2 {
  font-size: 1.75rem;
  margin-bottom: var(--spacing-sm);
}

.receive-card > p {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
}

/* Code Input */
.code-input-group {
  margin: var(--spacing-lg) 0;
}

.code-input {
  width: 100%;
  max-width: 280px;
  padding: var(--spacing-md) var(--spacing-lg);
  font-size: 2rem;
  font-weight: 700;
  text-align: center;
  letter-spacing: 0.5em;
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  color: var(--text-primary);
  transition: all var(--transition-normal);
  font-family: 'Courier New', monospace;
}

.code-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
  background: var(--bg-tertiary);
}

.code-input::placeholder {
  color: var(--text-muted);
  letter-spacing: 0.3em;
}

.help-text {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: var(--spacing-md);
}

.result-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-xl);
  text-align: center;
  animation: slideUp 0.4s ease;
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.success-icon {
  width: 96px;
  height: 96px;
  margin: 0 auto var(--spacing-lg);
  border-radius: 50%;
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.1), rgba(16, 185, 129, 0.2));
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--success);
  animation: scaleIn 0.5s ease 0.2s both;
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.5);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.result-card h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-sm);
  color: var(--success);
}

.result-message {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
}

.code-display {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  margin: var(--spacing-lg) 0;
  padding: var(--spacing-lg);
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-sm);
}

.code {
  font-size: 2.5rem;
  font-weight: 700;
  font-family: 'Courier New', monospace;
  letter-spacing: 0.2em;
  color: var(--accent-primary);
  user-select: all;
}

.expiry-notice {
  font-size: 0.9rem;
  color: var(--warning);
  margin: var(--spacing-md) 0 var(--spacing-lg);
}

.download-status {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md);
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.1), rgba(16, 185, 129, 0.2));
  border: 1px solid var(--success);
  border-radius: var(--border-radius-sm);
  color: var(--success);
  font-size: 0.95rem;
  font-weight: 600;
  margin: var(--spacing-md) 0;
  animation: slideUp 0.4s ease;
}

.download-status svg {
  flex-shrink: 0;
  stroke: var(--success);
}

.error-card {
  background: var(--bg-card);
  border: 1px solid var(--error);
  border-radius: var(--border-radius);
  padding: var(--spacing-xl);
  text-align: center;
  animation: shake 0.5s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-10px); }
  75% { transform: translateX(10px); }
}

.error-card svg {
  margin-bottom: var(--spacing-md);
}

.error-card p {
  color: var(--error);
  font-size: 1rem;
  margin-bottom: var(--spacing-lg);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  transition: all var(--transition-normal);
  text-decoration: none;
  font-family: inherit;
  white-space: nowrap;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

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

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

.btn-primary {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover:not(:disabled) {
  box-shadow: var(--shadow-lg), var(--shadow-glow);
  transform: translateY(-2px);
}

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

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

.btn-large {
  width: 100%;
  padding: var(--spacing-md) var(--spacing-lg);
  font-size: 1.1rem;
  min-height: 56px;
}

.btn-icon {
  padding: var(--spacing-sm);
  width: 44px;
  height: 44px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
}

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

.btn-icon svg {
  stroke: currentColor;
}

.spinner {
  width: 20px;
  height: 20px;
  border: 3px solid rgba(255, 255, 255, 0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.footer {
  text-align: center;
  padding: var(--spacing-lg) 0;
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-top: auto;
}

@media (hover: none) and (pointer: coarse) {
  .btn {
    min-height: 48px;
    min-width: 48px;
  }
  
  .card {
    min-height: 200px;
  }
}

*:focus-visible {
  outline: 2px solid var(--accent-primary);
  outline-offset: 2px;
}

button:focus-visible,
a:focus-visible,
input:focus-visible {
  outline: 2px solid var(--accent-primary);
  outline-offset: 2px;
}

.text-center {
  text-align: center;
}

.mt-lg {
  margin-top: var(--spacing-lg);
}

.mb-lg {
  margin-bottom: var(--spacing-lg);
}

@media (max-width: 480px) {
  .logo h1 {
    font-size: 1.75rem;
  }
  
  .card h2 {
    font-size: 1.25rem;
  }
  
  .code {
    font-size: 2rem;
  }
  
  .code-input {
    font-size: 1.5rem;
    letter-spacing: 0.3em;
  }
}

@media (min-width: 768px) {
  .upload-card,
  .receive-card,
  .result-card {
    padding: var(--spacing-xl);
  }
  
  .drop-zone {
    min-height: 360px;
  }
}


.text-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-md);
  animation: slideUp var(--transition-normal);
}

.text-icon {
  width: 80px;
  height: 80px;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--spacing-md);
}

.text-icon svg {
  stroke: white;
  stroke-width: 1.5;
}

.text-card h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-xs);
  text-align: center;
}

.text-card p {
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: var(--spacing-lg);
}

.text-input-container {
  margin-bottom: var(--spacing-lg);
}

.text-input {
  width: 100%;
  min-height: 200px;
  max-height: 400px;
  padding: var(--spacing-md);
  background: var(--bg-tertiary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: 0.95rem;
  line-height: 1.6;
  resize: vertical;
  transition: border-color var(--transition-fast);
}

.text-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

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

.char-counter {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: var(--spacing-xs);
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.size-warning {
  color: var(--error);
  font-weight: 600;
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

.text-display-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-md);
  animation: slideUp var(--transition-normal);
}

.text-display-card h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-lg);
  text-align: center;
}

.text-display-container {
  margin-bottom: var(--spacing-lg);
}

.text-display {
  width: 100%;
  min-height: 200px;
  max-height: 500px;
  padding: var(--spacing-md);
  background: var(--bg-tertiary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: 0.95rem;
  line-height: 1.6;
  resize: vertical;
}

.text-display:focus {
  outline: none;
  border-color: var(--accent-primary);
}

.text-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-md);
  margin-top: var(--spacing-md);
}

.copy-success {
  color: var(--success);
  font-weight: 600;
  animation: fadeIn var(--transition-fast);
}

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


.card-send-text {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.05));
}

.card-send-text:hover {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.15), rgba(139, 92, 246, 0.1));
  border-color: var(--accent-primary);
}

.card-receive-text {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.1), rgba(5, 150, 105, 0.05));
}

.card-receive-text:hover {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.15), rgba(5, 150, 105, 0.1));
  border-color: var(--success);
}

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

.btn-disabled:hover {
  transform: none;
  box-shadow: var(--shadow-sm);
}

@media print {
  body {
    background: white;
    color: black;
  }
  
  .back-btn,
  .btn,
  .footer {
    display: none;
  }
}