@import url('https://fonts.googleapis.com/css2?family=Space+Mono:ital,wght@0,400;0,700;1,400&family=Syne:wght@400;700;800&display=swap');

/* ── CSS Custom Properties ── */
:root {
  --color-bg:        #0a0a14;
  --color-surface:   #13131f;
  --color-card:      #1c1c2e;
  --color-card-face: #252540;
  --color-accent:    #7c6af7;
  --color-accent2:   #f76a8c;
  --color-accent3:   #6af7c8;
  --color-text:      #e8e8f4;
  --color-muted:     #6b6b8a;
  --color-success:   #4ade80;
  --color-warning:   #facc15;
  --spacing-sm:      0.5rem;
  --spacing-md:      1rem;
  --spacing-lg:      2rem;
  --spacing-xl:      3rem;
  --radius-card:     16px;
  --radius-sm:       8px;
  --transition-base: 0.25s ease;
  --shadow-glow:     0 0 24px rgba(124, 106, 247, 0.35);
  --shadow-card:     0 4px 20px rgba(0,0,0,0.5);
  --font-display:    'Syne', sans-serif;
  --font-mono:       'Space Mono', monospace;
}

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

html {
  scroll-behavior: smooth;
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-mono);
  font-size: 1rem;
  line-height: 1.6;
  min-height: 100vh;
  background-image:
    radial-gradient(ellipse at 20% 20%, rgba(124,106,247,0.12) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 80%, rgba(247,106,140,0.08) 0%, transparent 50%),
    url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%237c6af7' fill-opacity='0.03'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

/* ── Typography ── */
h1, h2, h3, .display {
  font-family: var(--font-display);
  letter-spacing: -0.02em;
}

/* ── Navbar ── */
.navbar {
  background: rgba(10, 10, 20, 0.85) !important;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(124,106,247,0.2);
  padding: 0.75rem var(--spacing-md);
}

.navbar-brand {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.4rem;
  color: var(--color-text) !important;
  letter-spacing: -0.03em;
}

.navbar-brand span {
  color: var(--color-accent);
}

.nav-link {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--color-muted) !important;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.5rem 0.9rem !important;
  border-radius: var(--radius-sm);
  transition: color var(--transition-base), background var(--transition-base);
}

.nav-link:hover,
.nav-link:focus {
  color: var(--color-text) !important;
  background: rgba(124,106,247,0.12);
}

.navbar-toggler {
  border-color: rgba(124,106,247,0.4);
}

.navbar-toggler-icon {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba%28124, 106, 247, 0.9%29' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");
}

/* ── Main Layout ── */
main {
  padding: var(--spacing-lg) var(--spacing-md);
  max-width: 1100px;
  margin: 0 auto;
}

/* ── Hero / Title Area ── */
.game-hero {
  text-align: center;
  padding: var(--spacing-lg) 0 var(--spacing-md);
}

.game-hero h1 {
  font-size: clamp(2rem, 6vw, 4rem);
  font-weight: 800;
  background: linear-gradient(135deg, var(--color-text), var(--color-accent), var(--color-accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--spacing-sm);
}

.game-hero .tagline {
  color: var(--color-muted);
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

/* ── Stats Bar ── */
.stats-bar {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  flex-wrap: wrap;
  margin: var(--spacing-md) 0;
}

.stat-chip {
  background: var(--color-surface);
  border: 1px solid rgba(124,106,247,0.2);
  border-radius: 999px;
  padding: 0.4rem 1.1rem;
  font-size: 0.8rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: border-color var(--transition-base);
}

.stat-chip:hover {
  border-color: rgba(124,106,247,0.5);
}

.stat-chip .label {
  color: var(--color-muted);
  text-transform: uppercase;
  font-size: 0.65rem;
  letter-spacing: 0.1em;
}

.stat-chip .value {
  color: var(--color-accent);
  font-weight: 700;
}

/* aria-live region for score changes */
#live-announce {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}

/* ── Game Board ── */
#game-board {
  display: grid;
  gap: var(--spacing-md);
  margin: var(--spacing-lg) auto;
  max-width: 900px;
  /* columns set by JS based on difficulty */
}

/* ── Card Component ── */
.card-wrapper {
  perspective: 900px;
  aspect-ratio: 1;
  cursor: pointer;
}

.memory-card {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.4, 0, 0.2, 1);
  border-radius: var(--radius-card);
}

/* Advanced selector: attribute selector for flipped state */
.memory-card[data-flipped="true"] {
  transform: rotateY(180deg);
}

.memory-card[data-matched="true"] {
  animation: matchPulse 0.6s ease forwards;
}

.card-back,
.card-front {
  position: absolute;
  inset: 0;
  border-radius: var(--radius-card);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-card);
}

/* Card back face */
.card-back {
  background: var(--color-card);
  border: 1px solid rgba(124,106,247,0.25);
  transition: border-color var(--transition-base), box-shadow var(--transition-base);
}

.card-back::before {
  content: '✦';
  font-size: clamp(1.4rem, 4vw, 2.2rem);
  color: rgba(124,106,247,0.4);
  transition: color var(--transition-base);
}

/* nth-child for alternating card back pattern */
.card-wrapper:nth-child(odd) .card-back::before {
  content: '✧';
  color: rgba(247,106,140,0.35);
}

.card-wrapper:hover .card-back {
  border-color: rgba(124,106,247,0.6);
  box-shadow: var(--shadow-glow);
}

.card-wrapper:hover .card-back::before {
  color: rgba(124,106,247,0.8);
}

/* Card front face */
.card-front {
  background: var(--color-card-face);
  border: 1px solid rgba(124,106,247,0.35);
  transform: rotateY(180deg);
  flex-direction: column;
  gap: 0.4rem;
}

.card-emoji {
  font-size: clamp(1.8rem, 5vw, 3rem);
  line-height: 1;
}

.card-label {
  font-size: clamp(0.55rem, 1.5vw, 0.75rem);
  color: var(--color-muted);
  text-align: center;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 0 0.4rem;
}

/* Matched card state */
.memory-card[data-matched="true"] .card-front {
  border-color: var(--color-accent3);
  background: rgba(106, 247, 200, 0.08);
}

/* ── Animations ── */
@keyframes matchPulse {
  0%   { box-shadow: 0 0 0 0 rgba(106,247,200,0.6); }
  50%  { box-shadow: 0 0 0 14px rgba(106,247,200,0); }
  100% { box-shadow: 0 0 0 0 rgba(106,247,200,0); }
}

@keyframes cardReveal {
  from {
    opacity: 0;
    transform: scale(0.8) translateY(16px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

.card-wrapper {
  animation: cardReveal 0.4s ease backwards;
}

/* Stagger card reveal using nth-child */
.card-wrapper:nth-child(1)  { animation-delay: 0.03s; }
.card-wrapper:nth-child(2)  { animation-delay: 0.06s; }
.card-wrapper:nth-child(3)  { animation-delay: 0.09s; }
.card-wrapper:nth-child(4)  { animation-delay: 0.12s; }
.card-wrapper:nth-child(5)  { animation-delay: 0.15s; }
.card-wrapper:nth-child(6)  { animation-delay: 0.18s; }
.card-wrapper:nth-child(7)  { animation-delay: 0.21s; }
.card-wrapper:nth-child(8)  { animation-delay: 0.24s; }
.card-wrapper:nth-child(9)  { animation-delay: 0.27s; }
.card-wrapper:nth-child(10) { animation-delay: 0.30s; }
.card-wrapper:nth-child(11) { animation-delay: 0.33s; }
.card-wrapper:nth-child(12) { animation-delay: 0.36s; }
.card-wrapper:nth-child(13) { animation-delay: 0.39s; }
.card-wrapper:nth-child(14) { animation-delay: 0.42s; }
.card-wrapper:nth-child(15) { animation-delay: 0.45s; }
.card-wrapper:nth-child(16) { animation-delay: 0.48s; }
.card-wrapper:nth-child(17) { animation-delay: 0.51s; }
.card-wrapper:nth-child(18) { animation-delay: 0.54s; }
.card-wrapper:nth-child(19) { animation-delay: 0.57s; }
.card-wrapper:nth-child(20) { animation-delay: 0.60s; }

/* ── Reduced motion ── */
@media (prefers-reduced-motion: reduce) {
  .memory-card {
    transition: none;
  }
  .card-wrapper {
    animation: none;
  }
  .memory-card[data-matched="true"] {
    animation: none;
    outline: 3px solid var(--color-accent3);
  }
  * {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* ── Controls ── */
.controls {
  display: flex;
  justify-content: center;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
  margin-bottom: var(--spacing-lg);
}

.btn-galactic {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.65rem 1.4rem;
  border-radius: 999px;
  border: 1px solid rgba(124,106,247,0.4);
  background: transparent;
  color: var(--color-text);
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.btn-galactic::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent2));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.btn-galactic:hover::before,
.btn-galactic:focus::before {
  opacity: 0.15;
}

.btn-galactic:hover,
.btn-galactic:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 16px rgba(124,106,247,0.3);
  outline: none;
}

.btn-galactic:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

.btn-galactic span {
  position: relative;
  z-index: 1;
}

.btn-galactic.primary {
  background: linear-gradient(135deg, var(--color-accent), #5b4fd4);
  border-color: transparent;
  color: #fff;
  font-weight: 700;
}

.btn-galactic.primary::before {
  display: none;
}

.btn-galactic.primary:hover {
  background: linear-gradient(135deg, #9588ff, var(--color-accent));
  transform: translateY(-1px);
  box-shadow: 0 6px 24px rgba(124,106,247,0.45);
}

/* ── Modal Customization ── */
.modal-content {
  background: var(--color-surface);
  border: 1px solid rgba(124,106,247,0.3);
  border-radius: var(--radius-card);
  color: var(--color-text);
}

.modal-header {
  border-bottom: 1px solid rgba(124,106,247,0.2);
}

.modal-footer {
  border-top: 1px solid rgba(124,106,247,0.2);
}

.modal-title {
  font-family: var(--font-display);
  font-weight: 800;
}

.btn-close {
  filter: invert(1);
}

/* ── Settings Form ── */
.settings-form label {
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--color-muted);
  margin-bottom: 0.3rem;
  display: block;
}

/* Adjacent sibling: label + input */
.settings-form label + input,
.settings-form label + select {
  border: 1px solid rgba(124,106,247,0.3);
  background: var(--color-card);
  color: var(--color-text);
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.85rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  width: 100%;
  transition: border-color var(--transition-base);
}

.settings-form label + input:focus,
.settings-form label + select:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(124,106,247,0.2);
}

.settings-form select option {
  background: var(--color-card);
  color: var(--color-text);
}

/* Constraint Validation styling */
.settings-form input:invalid:not(:placeholder-shown),
.settings-form input.was-validated:invalid {
  border-color: var(--color-accent2);
}

.settings-form input:valid:not(:placeholder-shown) {
  border-color: var(--color-accent3);
}

.invalid-feedback {
  color: var(--color-accent2);
  font-size: 0.72rem;
  margin-top: 0.25rem;
  display: none;
}

.was-validated ~ .invalid-feedback,
.field-error .invalid-feedback {
  display: block;
}

/* ── Progress Bar ── */
.progress-section {
  margin: var(--spacing-md) auto;
  max-width: 500px;
  text-align: center;
}

.progress-label {
  font-size: 0.75rem;
  color: var(--color-muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.progress {
  background: var(--color-card);
  border-radius: 999px;
  height: 8px;
  overflow: hidden;
}

.progress-bar {
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent2));
  transition: width 0.4s ease;
  border-radius: 999px;
}

/* ── Win Screen (Toast-like overlay) ── */
#win-toast {
  position: fixed;
  bottom: var(--spacing-lg);
  left: 50%;
  transform: translateX(-50%) translateY(120px);
  background: var(--color-surface);
  border: 1px solid var(--color-accent3);
  border-radius: var(--radius-card);
  padding: var(--spacing-md) var(--spacing-lg);
  text-align: center;
  z-index: 999;
  min-width: 280px;
  box-shadow: 0 8px 40px rgba(106,247,200,0.2);
  transition: transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

#win-toast.show {
  transform: translateX(-50%) translateY(0);
}

#win-toast h2 {
  font-family: var(--font-display);
  font-size: 1.6rem;
  color: var(--color-accent3);
  margin-bottom: 0.3rem;
}

#win-toast p {
  font-size: 0.82rem;
  color: var(--color-muted);
}

/* ── High Score Badge ── */
.high-score-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: rgba(250,204,21,0.1);
  border: 1px solid rgba(250,204,21,0.35);
  border-radius: 999px;
  padding: 0.25rem 0.85rem;
  font-size: 0.75rem;
  color: var(--color-warning);
  letter-spacing: 0.06em;
}

/* ── Instructions Section ── */
.instructions {
  background: var(--color-surface);
  border: 1px solid rgba(124,106,247,0.15);
  border-radius: var(--radius-card);
  padding: var(--spacing-lg);
  margin: var(--spacing-lg) 0;
}

.instructions h2 {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-md);
  color: var(--color-accent);
}

/* Child combinator: direct li children */
.instructions > ol > li {
  padding: 0.3rem 0;
  color: var(--color-muted);
  font-size: 0.85rem;
}

.instructions > ol > li strong {
  color: var(--color-text);
}

/* ── Theme Variants ── */
body.theme-nebula {
  --color-accent:  #f76ac8;
  --color-accent2: #c86af7;
  --color-accent3: #f7a96a;
}

body.theme-aurora {
  --color-bg:      #020d0a;
  --color-surface: #071410;
  --color-card:    #0d1f1a;
  --color-accent:  #34d399;
  --color-accent2: #06b6d4;
  --color-accent3: #a3e635;
}

/* ── Footer ── */
footer {
  background: var(--color-surface);
  border-top: 1px solid rgba(124,106,247,0.15);
  padding: var(--spacing-lg) var(--spacing-md);
  text-align: center;
  margin-top: var(--spacing-xl);
}

footer a {
  color: var(--color-muted);
  font-size: 0.75rem;
  text-decoration: none;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin: 0 0.6rem;
  transition: color var(--transition-base);
}

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

footer .footer-brand {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1rem;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
  display: block;
}

footer .footer-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.25rem var(--spacing-sm);
  margin-top: var(--spacing-sm);
}

/* ── Focus Outlines (Keyboard Nav) ── */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

.card-wrapper:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
  border-radius: var(--radius-card);
}

/* ── Responsive ── */
@media (max-width: 576px) {
  .stats-bar {
    gap: var(--spacing-sm);
  }

  .stat-chip {
    font-size: 0.72rem;
    padding: 0.3rem 0.8rem;
  }
}