/* ========================================================================== 
   Variables
   ========================================================================== */
:root {
  /* Color palette */
  --color-bg: #050816;
  --color-surface: #070b1e;
  --color-surface-soft: #0b1126;
  --color-text: #f9fbff;
  --color-text-muted: #a7b3d4;
  --color-primary: #3b82f6;
  --color-primary-soft: rgba(59, 130, 246, 0.15);
  --color-primary-strong: #2563eb;
  --color-success: #22c55e;
  --color-warning: #fbbf24;
  --color-danger: #ef4444;

  --gray-50: #f9fafb;
  --gray-100: #e5e7eb;
  --gray-200: #e5e7f0;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2933;
  --gray-900: #111827;

  /* Typography */
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "JetBrains Mono", Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

  --font-size-xs: 0.75rem;   /* 12px */
  --font-size-sm: 0.875rem;  /* 14px */
  --font-size-base: 1rem;    /* 16px */
  --font-size-lg: 1.125rem;  /* 18px */
  --font-size-xl: 1.25rem;   /* 20px */
  --font-size-2xl: 1.5rem;   /* 24px */
  --font-size-3xl: 1.875rem; /* 30px */
  --font-size-4xl: 2.25rem;  /* 36px */
  --font-size-5xl: 3rem;     /* 48px */

  --line-height-tight: 1.15;
  --line-height-normal: 1.6;
  --line-height-relaxed: 1.8;

  /* Spacing scale (0–96px) */
  --space-0: 0;
  --space-1: 0.25rem;  /* 4px */
  --space-2: 0.5rem;   /* 8px */
  --space-3: 0.75rem;  /* 12px */
  --space-4: 1rem;     /* 16px */
  --space-5: 1.25rem;  /* 20px */
  --space-6: 1.5rem;   /* 24px */
  --space-8: 2rem;     /* 32px */
  --space-10: 2.5rem;  /* 40px */
  --space-12: 3rem;    /* 48px */
  --space-16: 4rem;    /* 64px */
  --space-20: 5rem;    /* 80px */
  --space-24: 6rem;    /* 96px */

  /* Radius */
  --radius-sm: 0.375rem;   /* 6px */
  --radius-md: 0.75rem;    /* 12px */
  --radius-lg: 1.25rem;    /* 20px */
  --radius-full: 9999px;

  /* Shadows */
  --shadow-soft: 0 18px 45px rgba(15, 23, 42, 0.45);
  --shadow-subtle: 0 10px 30px rgba(15, 23, 42, 0.35);
  --shadow-focus: 0 0 0 2px rgba(15, 23, 42, 0.9), 0 0 0 4px rgba(59, 130, 246, 0.8);

  /* Transitions */
  --transition-fast: 120ms ease-out;
  --transition-base: 180ms ease-out;
  --transition-slow: 260ms ease-out;

  /* Layout */
  --layout-max-width: 1120px;
  --layout-gutter: var(--space-4);
}

/* ========================================================================== 
   Reset / Normalize
   ========================================================================== */
*, *::before, *::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  text-size-adjust: 100%;
}

body {
  min-height: 100vh;
}

h1,
 h2,
 h3,
 h4,
 h5,
 h6,
 p,
 figure,
 blockquote,
 dl,
 dd {
  margin: 0;
}

ul,
ol {
  margin: 0;
  padding: 0;
}

button,
input,
select,
textarea {
  font: inherit;
  color: inherit;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

img {
  height: auto;
}

a {
  color: inherit;
  text-decoration: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

/* ========================================================================== 
   Base Styles
   ========================================================================== */
body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  color: var(--color-text);
  background:
    radial-gradient(circle at 0% 0%, rgba(56, 189, 248, 0.16), transparent 55%),
    radial-gradient(circle at 100% 100%, rgba(59, 130, 246, 0.25), transparent 55%),
    linear-gradient(135deg, #020617 0%, #020617 35%, #020617 100%);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

main {
  display: block;
}

h1,
 h2,
 h3,
 h4,
 h5,
 h6 {
  font-weight: 700;
  color: var(--color-text);
  line-height: var(--line-height-tight);
  letter-spacing: -0.02em;
}

h1 {
  font-size: clamp(2.4rem, 4vw, 3.4rem);
  margin-bottom: var(--space-4);
}

h2 {
  font-size: clamp(1.8rem, 3vw, 2.4rem);
  margin-bottom: var(--space-3);
}

h3 {
  font-size: clamp(1.35rem, 2.3vw, 1.7rem);
  margin-bottom: var(--space-2);
}

h4 {
  font-size: 1.1rem;
  margin-bottom: var(--space-2);
}

p {
  margin-bottom: var(--space-3);
  color: var(--color-text-muted);
}

strong {
  font-weight: 600;
}

code,
pre {
  font-family: var(--font-mono);
}

pre {
  background: rgba(15, 23, 42, 0.85);
  padding: var(--space-3);
  border-radius: var(--radius-md);
  overflow-x: auto;
}

a {
  position: relative;
  transition: color var(--transition-base);
}

a:hover {
  color: var(--color-primary);
}

a:focus-visible {
  outline: none;
}

/* ========================================================================== 
   Accessibility & Motion
   ========================================================================== */
:focus-visible {
  outline: none;
  box-shadow: var(--shadow-focus);
  border-radius: 0.35rem;
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

/* ========================================================================== 
   Utilities
   ========================================================================== */

/* Layout */
.container {
  width: 100%;
  max-width: var(--layout-max-width);
  margin-inline: auto;
  padding-inline: var(--layout-gutter);
}

.section {
  padding-block: clamp(3rem, 8vh, 5rem);
}

.section--tight {
  padding-block: clamp(2.5rem, 6vh, 4rem);
}

/* Flex helpers */
.flex {
  display: flex;
}

.inline-flex {
  display: inline-flex;
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.flex-column {
  display: flex;
  flex-direction: column;
}

.gap-xs {
  gap: var(--space-2);
}

.gap-sm {
  gap: var(--space-3);
}

.gap-md {
  gap: var(--space-4);
}

.gap-lg {
  gap: var(--space-6);
}

/* Grid helpers */
.grid {
  display: grid;
  gap: var(--space-4);
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-6);
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-6);
}

@media (max-width: 768px) {
  .grid-2,
  .grid-3 {
    grid-template-columns: minmax(0, 1fr);
  }
}

/* Text alignment */
.text-center {
  text-align: center;
}

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

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

/* Width helpers */
.w-full {
  width: 100%;
}

/* Spacing utilities (selected) */
.mt-0 { margin-top: 0; }
.mt-xs { margin-top: var(--space-2); }
.mt-sm { margin-top: var(--space-3); }
.mt-md { margin-top: var(--space-4); }
.mt-lg { margin-top: var(--space-6); }

.mb-0 { margin-bottom: 0; }
.mb-xs { margin-bottom: var(--space-2); }
.mb-sm { margin-bottom: var(--space-3); }
.mb-md { margin-bottom: var(--space-4); }
.mb-lg { margin-bottom: var(--space-6); }

.pt-section { padding-top: clamp(3rem, 8vh, 5rem); }
.pb-section { padding-bottom: clamp(3rem, 8vh, 5rem); }

/* Screen reader only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ========================================================================== 
   Components
   ========================================================================== */

/* Buttons - base styles tuned for hero CTA (Download & Explore) */
.btn {
  --btn-bg: var(--color-surface-soft);
  --btn-bg-hover: #0f172a;
  --btn-color: var(--color-text);
  --btn-border: transparent;

  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding-inline: 1.4rem;
  padding-block: 0.8rem;
  border-radius: var(--radius-full);
  border: 1px solid var(--btn-border);
  background: var(--btn-bg);
  color: var(--btn-color);
  font-weight: 500;
  font-size: 0.95rem;
  letter-spacing: 0.02em;
  text-decoration: none;
  cursor: pointer;
  transition:
    background-color var(--transition-base),
    color var(--transition-base),
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    transform var(--transition-fast);
  box-shadow: 0 0 0 1px rgba(148, 163, 184, 0.12);
}

.btn:hover {
  background: var(--btn-bg-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-subtle);
}

.btn:active {
  transform: translateY(0);
  box-shadow: 0 6px 20px rgba(15, 23, 42, 0.55);
}

.btn:focus-visible {
  box-shadow: var(--shadow-focus);
}

.btn--primary {
  --btn-bg: linear-gradient(135deg, #1d4ed8, #3b82f6, #22d3ee);
  --btn-bg-hover: linear-gradient(135deg, #1e40af, #2563eb, #06b6d4);
  --btn-color: #f9fafb;
  --btn-border: rgba(191, 219, 254, 0.8);
}

.btn--secondary {
  --btn-bg: rgba(15, 23, 42, 0.75);
  --btn-bg-hover: rgba(15, 23, 42, 0.95);
  --btn-color: var(--color-text-muted);
  --btn-border: rgba(148, 163, 184, 0.4);
}

.btn--ghost {
  --btn-bg: transparent;
  --btn-bg-hover: rgba(15, 23, 42, 0.75);
  --btn-color: var(--color-text-muted);
  --btn-border: rgba(148, 163, 184, 0.3);
}

.btn--sm {
  padding-block: 0.55rem;
  padding-inline: 1.1rem;
  font-size: 0.85rem;
}

.btn--icon-left svg,
.btn--icon-right svg {
  width: 1.15rem;
  height: 1.15rem;
  flex-shrink: 0;
}

.btn--icon-left svg {
  margin-right: 0.15rem;
}

.btn[disabled],
.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  box-shadow: none;
  transform: none;
}

/* Inputs */
.input,
select,
textarea {
  width: 100%;
  padding: 0.7rem 0.9rem;
  border-radius: 0.6rem;
  border: 1px solid rgba(148, 163, 184, 0.45);
  background: radial-gradient(circle at top left, rgba(59, 130, 246, 0.14), transparent 55%),
              rgba(15, 23, 42, 0.95);
  color: var(--color-text);
  font-size: 0.95rem;
  outline: none;
  transition:
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    background-color var(--transition-base),
    transform var(--transition-fast);
}

.input::placeholder,
textarea::placeholder {
  color: rgba(148, 163, 184, 0.85);
}

.input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  border-color: rgba(129, 140, 248, 0.9);
  box-shadow: 0 0 0 1px rgba(129, 140, 248, 0.9), 0 0 30px rgba(59, 130, 246, 0.38);
  transform: translateY(-1px);
}

.input[disabled],
textarea[disabled],
select[disabled] {
  opacity: 0.6;
  cursor: not-allowed;
}

label {
  display: block;
  margin-bottom: 0.3rem;
  font-size: 0.85rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: rgba(148, 163, 184, 0.95);
}

/* Card - for puzzle types, difficulty levels, mechanics blocks */
.card {
  position: relative;
  padding: var(--space-5);
  border-radius: var(--radius-lg);
  background: radial-gradient(circle at top left, rgba(59, 130, 246, 0.22), transparent 60%),
              radial-gradient(circle at bottom right, rgba(15, 23, 42, 0.95), rgba(15, 23, 42, 0.98));
  border: 1px solid rgba(148, 163, 184, 0.32);
  box-shadow: var(--shadow-soft);
  overflow: hidden;
}

.card::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: linear-gradient(120deg, rgba(79, 70, 229, 0.2) 0, transparent 40%, transparent 60%, rgba(56, 189, 248, 0.25) 100%);
  opacity: 0;
  mix-blend-mode: screen;
  transition: opacity var(--transition-slow);
  pointer-events: none;
}

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

.card--subtle {
  padding: var(--space-4);
  background: rgba(15, 23, 42, 0.9);
  border-radius: var(--radius-md);
  border: 1px solid rgba(148, 163, 184, 0.28);
  box-shadow: 0 18px 45px rgba(15, 23, 42, 0.5);
}

.card__title {
  font-size: 1.1rem;
  margin-bottom: var(--space-2);
}

.card__meta {
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(148, 163, 184, 0.85);
  margin-bottom: var(--space-2);
}

.card__body {
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

/* Hero-specific helpers (for BRAIN PUZZLE WORLD) */
.hero {
  padding-block: clamp(4rem, 12vh, 6rem);
}

.hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr);
  gap: clamp(2.8rem, 6vw, 4rem);
  align-items: center;
}

@media (max-width: 900px) {
  .hero__grid {
    grid-template-columns: minmax(0, 1fr);
  }
}

.hero__eyebrow {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: rgba(129, 140, 248, 0.95);
  margin-bottom: var(--space-2);
}

.hero__headline {
  font-size: clamp(2.6rem, 5vw, 3.6rem);
  line-height: 1.05;
  margin-bottom: var(--space-3);
}

.hero__subcopy {
  max-width: 32rem;
  color: var(--color-text-muted);
  margin-bottom: var(--space-5);
}

.hero__cta-group {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.9rem;
}

/* Badge-like pill for categories: logic challenges, progression, etc. */
.pill {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.8rem;
  border-radius: 999px;
  border: 1px solid rgba(129, 140, 248, 0.55);
  background: radial-gradient(circle at 0 0, rgba(56, 189, 248, 0.18), transparent 60%), rgba(15, 23, 42, 0.95);
  color: rgba(191, 219, 254, 0.98);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
}

.pill__dot {
  width: 0.4rem;
  height: 0.4rem;
  border-radius: 999px;
  background: conic-gradient(from 90deg, #22c55e, #22d3ee, #3b82f6, #22c55e);
}

/* Status labels */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.badge--success {
  background: rgba(22, 163, 74, 0.12);
  color: #4ade80;
}

.badge--warning {
  background: rgba(245, 158, 11, 0.16);
  color: #fcd34d;
}

.badge--danger {
  background: rgba(220, 38, 38, 0.14);
  color: #fca5a5;
}

/* Tag list for puzzle types / difficulty chips */
.chip-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}

.chip {
  padding: 0.25rem 0.7rem;
  border-radius: 999px;
  border: 1px solid rgba(148, 163, 184, 0.4);
  font-size: 0.78rem;
  color: rgba(226, 232, 240, 0.9);
  background: rgba(15, 23, 42, 0.9);
}

.chip--active {
  border-color: rgba(129, 140, 248, 0.9);
  background:
    radial-gradient(circle at 0 0, rgba(56, 189, 248, 0.2), transparent 60%),
    rgba(15, 23, 42, 0.95);
}

/* Progress / steps (for progression system) */
.progress-track {
  position: relative;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.progress-track__bar {
  position: relative;
  flex: 1;
  height: 0.22rem;
  border-radius: 999px;
  background: rgba(30, 64, 175, 0.5);
  overflow: hidden;
}

.progress-track__bar-fill {
  position: absolute;
  inset: 0;
  width: var(--progress, 40%);
  background: linear-gradient(90deg, #22c55e, #3b82f6, #22d3ee);
}

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

/* Timeline list for updates / new challenges */
.timeline {
  position: relative;
  padding-left: 1.4rem;
  border-left: 1px solid rgba(75, 85, 99, 0.9);
}

.timeline__item {
  position: relative;
  padding-bottom: 1.4rem;
}

.timeline__item::before {
  content: "";
  position: absolute;
  left: -0.52rem;
  top: 0.25rem;
  width: 0.7rem;
  height: 0.7rem;
  border-radius: 999px;
  background: radial-gradient(circle at 30% 10%, #e5f2ff, #60a5fa);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.35);
}

.timeline__item:last-child {
  padding-bottom: 0;
}

/* Subtle hover lift utility for interactive tiles */
.hover-lift {
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base),
    border-color var(--transition-base),
    background var(--transition-base);
}

.hover-lift:hover {
  transform: translateY(-4px);
  box-shadow: 0 24px 60px rgba(15, 23, 42, 0.75);
}

/* Footer */
.footer {
  border-top: 1px solid rgba(15, 23, 42, 0.9);
  padding-block: var(--space-4);
  background: radial-gradient(circle at top, rgba(15, 23, 42, 0.96), rgba(15, 23, 42, 1));
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.footer__link-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
}

.footer a {
  color: rgba(148, 163, 184, 0.9);
}

.footer a:hover {
  color: rgba(191, 219, 254, 0.98);
}