/* ============================================
   Caesar Cipher Tool — Design System
   Dark glassmorphism theme
   ============================================ */

/* --- Custom Properties --- */
:root {
  --bg-base: #0a0a0f;
  --bg-surface: rgba(255, 255, 255, 0.04);
  --bg-surface-hover: rgba(255, 255, 255, 0.07);
  --bg-input: rgba(255, 255, 255, 0.05);

  --border: rgba(255, 255, 255, 0.08);
  --border-focus: rgba(217, 70, 239, 0.5);

  --text-primary: #f0f0f5;
  --text-secondary: #9a9aaf;
  --text-muted: #5a5a70;

  --accent: #d946ef;
  --accent-hover: #e879f9;
  --accent-glow: rgba(217, 70, 239, 0.25);
  --accent-secondary: #7c3aed;

  --success: #34d399;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;

  --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.4),
                 0 0 0 1px var(--border);
  --transition: 200ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

/* --- Body & Background --- */
body {
  font-family: var(--font-sans);
  background: var(--bg-base);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

.bg-gradient {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(ellipse 60% 50% at 20% 20%, rgba(124, 58, 237, 0.12), transparent),
    radial-gradient(ellipse 50% 40% at 80% 80%, rgba(217, 70, 239, 0.10), transparent),
    radial-gradient(ellipse 40% 50% at 50% 50%, rgba(99, 102, 241, 0.06), transparent);
  animation: gradientShift 15s ease-in-out infinite alternate;
}

@keyframes gradientShift {
  0% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.8; transform: scale(1.05); }
  100% { opacity: 1; transform: scale(1); }
}

/* --- Layout --- */
.container {
  max-width: 640px;
  margin: 0 auto;
  padding: 40px 20px 32px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* --- Header --- */
.header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 32px;
}

.logo {
  flex-shrink: 0;
}

.title {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--text-primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 400;
  margin-top: 2px;
}

/* --- Glass Card --- */
.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  gap: 24px;
  flex: 1 0 auto;
}

/* --- Shift Control --- */
.shift-control {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.shift-label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.shift-value {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 40px;
  height: 28px;
  background: linear-gradient(135deg, var(--accent-secondary), var(--accent));
  color: #fff;
  font-size: 0.85rem;
  font-weight: 600;
  border-radius: 6px;
  font-family: var(--font-mono);
}

/* Range Slider */
.slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  background: var(--bg-input);
  border-radius: 3px;
  outline: none;
  cursor: pointer;
  transition: background var(--transition);
}

.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--bg-base);
  box-shadow: 0 0 12px var(--accent-glow), 0 2px 6px rgba(0, 0, 0, 0.3);
  cursor: grab;
  transition: transform var(--transition), box-shadow var(--transition);
}

.slider::-webkit-slider-thumb:hover {
  transform: scale(1.15);
  box-shadow: 0 0 20px var(--accent-glow), 0 2px 8px rgba(0, 0, 0, 0.4);
}

.slider::-webkit-slider-thumb:active {
  cursor: grabbing;
  transform: scale(1.05);
}

.slider::-moz-range-thumb {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--bg-base);
  box-shadow: 0 0 12px var(--accent-glow), 0 2px 6px rgba(0, 0, 0, 0.3);
  cursor: grab;
  transition: transform var(--transition), box-shadow var(--transition);
}

.slider::-moz-range-thumb:hover {
  transform: scale(1.15);
}

.slider-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.7rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

/* --- Textareas --- */
.textareas {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.textarea-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.textarea-label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.textarea {
  width: 100%;
  padding: 14px 16px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.6;
  resize: vertical;
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition), background var(--transition);
}

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

.textarea:hover {
  background: var(--bg-surface-hover);
}

.textarea:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--accent-glow);
  background: var(--bg-surface-hover);
}

.textarea.output {
  background: rgba(124, 58, 237, 0.06);
  cursor: default;
}

.textarea.output:focus {
  border-color: var(--border);
  box-shadow: none;
}

.char-count {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-align: right;
  font-family: var(--font-mono);
}

/* --- Buttons --- */
.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 10px 18px;
  border-radius: var(--radius-sm);
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 500;
  border: none;
  cursor: pointer;
  outline: none;
  transition: all var(--transition);
  white-space: nowrap;
  user-select: none;
}

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

.btn svg {
  flex-shrink: 0;
}

/* Primary — Encrypt */
.btn-primary {
  background: linear-gradient(135deg, var(--accent-secondary), var(--accent));
  color: #fff;
  box-shadow: 0 2px 12px var(--accent-glow);
}

.btn-primary:hover {
  box-shadow: 0 4px 20px var(--accent-glow);
  transform: translateY(-1px);
  filter: brightness(1.1);
}

.btn-primary:active {
  transform: translateY(0);
  filter: brightness(0.95);
}

/* Secondary — Decrypt */
.btn-secondary {
  background: var(--bg-surface-hover);
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.15);
  transform: translateY(-1px);
}

.btn-secondary:active {
  transform: translateY(0);
}

/* Ghost — Copy / Clear */
.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  padding: 10px 14px;
}

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

.btn-ghost.copied {
  color: var(--success);
}

/* --- Keyboard Shortcuts --- */
.shortcuts {
  display: flex;
  gap: 18px;
  justify-content: center;
  flex-wrap: wrap;
}

.shortcut {
  font-size: 0.72rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 4px;
}

kbd {
  display: inline-block;
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  background: var(--bg-surface-hover);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text-secondary);
}

/* --- Footer --- */
.footer {
  margin-top: 28px;
  text-align: center;
  padding: 16px 0;
  font-size: 0.78rem;
  color: var(--text-muted);
}

.footer a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}

.footer a:hover {
  color: var(--accent-hover);
}

/* --- Animations --- */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.card {
  animation: fadeIn 0.5s ease-out;
}

.header {
  animation: fadeIn 0.4s ease-out;
}

/* Output flash on process */
.textarea.flash {
  animation: outputFlash 0.4s ease-out;
}

@keyframes outputFlash {
  0%   { box-shadow: 0 0 0 3px var(--accent-glow); }
  100% { box-shadow: none; }
}

/* --- Responsive --- */
@media (max-width: 520px) {
  .container {
    padding: 24px 14px 20px;
  }

  .card {
    padding: 20px 16px;
    border-radius: var(--radius-md);
  }

  .title {
    font-size: 1.3rem;
  }

  .actions {
    flex-direction: column;
  }

  .btn {
    justify-content: center;
  }

  .textarea {
    font-size: 0.82rem;
  }
}

@media (min-width: 521px) and (max-width: 768px) {
  .container {
    padding: 32px 18px 24px;
  }
}