/* ===== CSS Variables (Design Tokens) ===== */
:root {
  /* Colors */
  --color-primary: #3b82f6;
  --color-primary-hover: #2563eb;
  --color-primary-light: #dbeafe;
  --color-success: #22c55e;
  --color-success-hover: #16a34a;
  --color-success-light: #dcfce7;
  --color-danger: #ef4444;
  --color-danger-hover: #dc2626;
  --color-danger-light: #fee2e2;
  --color-warning: #f59e0b;
  --color-warning-hover: #d97706;
  --color-warning-light: #fef3c7;
  --color-secondary: #64748b;
  --color-secondary-hover: #475569;

  /* Backgrounds */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --bg-card: #ffffff;

  /* Text */
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --text-inverse: #ffffff;

  /* Borders */
  --border-color: #e2e8f0;
  --border-color-dark: #cbd5e1;

  /* Spacing scale */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;

  /* Border radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 200ms ease;
  --transition-slow: 300ms ease;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.625;

  /* Layout */
  --max-width-content: 960px;
  --max-width-card: 600px;
  --header-height: 64px;
}

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

/* ===== Body & Layout ===== */
body {
  margin: 0;
  padding: 0;
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  min-height: 100vh;
}

main {
  margin: 0 auto;
  padding: var(--space-6) var(--space-4);
  max-width: var(--max-width-content);
}

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-4);
  font-weight: 600;
  line-height: var(--line-height-tight);
  color: var(--text-primary);
}

h1 {
  font-size: var(--font-size-3xl);
  text-align: center;
}

h2 {
  font-size: var(--font-size-2xl);
}

h3 {
  font-size: var(--font-size-xl);
}

p {
  margin: 0 0 var(--space-4);
  color: var(--text-secondary);
}

/* ===== Header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--bg-primary);
  padding: 0 var(--space-6);
  height: var(--header-height);
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
}

.home-button {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  text-decoration: none;
  transition: all var(--transition-fast);
}

.home-button:hover {
  background-color: var(--bg-tertiary);
  color: var(--color-primary);
}

.home-button svg {
  width: 24px;
  height: 24px;
}

.site-title {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
  letter-spacing: -0.025em;
}

.site-title:hover {
  color: var(--color-primary);
}

/* Hamburger Menu */
.menu-toggle {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  padding: 0;
  background: transparent;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background-color var(--transition-fast);
}

.menu-toggle:hover {
  background-color: var(--bg-tertiary);
}

.menu-toggle .bar {
  width: 20px;
  height: 2px;
  background-color: var(--text-primary);
  border-radius: var(--radius-full);
  transition: all var(--transition-normal);
}

.menu-toggle .bar + .bar {
  margin-top: 5px;
}

/* Menu toggle animation */
.menu-toggle[aria-expanded="true"] .bar:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.menu-toggle[aria-expanded="true"] .bar:nth-child(2) {
  opacity: 0;
}

.menu-toggle[aria-expanded="true"] .bar:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* Navigation Menu */
.menu {
  position: absolute;
  top: var(--header-height);
  right: 0;
  left: 0;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-lg);
  padding: var(--space-4) 0;
  animation: slideDown var(--transition-normal) ease;
}

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

.menu[hidden] {
  display: none;
}

.menu ul {
  list-style: none;
  margin: 0;
  padding: 0;
  max-width: var(--max-width-content);
  margin: 0 auto;
}

.menu li {
  margin: 0;
}

.menu a {
  display: block;
  padding: var(--space-3) var(--space-6);
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.menu a:hover {
  background-color: var(--bg-tertiary);
  color: var(--color-primary);
}

/* ===== Horizontal Navigation Bar ===== */
.nav-bar {
  background-color: var(--color-primary);
  padding: 0;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: var(--color-primary-hover) var(--color-primary);
}

.nav-bar::-webkit-scrollbar {
  height: 4px;
}

.nav-bar::-webkit-scrollbar-track {
  background: var(--color-primary);
}

.nav-bar::-webkit-scrollbar-thumb {
  background: var(--color-primary-hover);
  border-radius: var(--radius-full);
}

.nav-bar ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  justify-content: center;
  max-width: none;
  text-align: center;
}

.nav-bar li {
  margin: 0;
  flex-shrink: 0;
}

.nav-bar a {
  display: block;
  padding: var(--space-3) var(--space-4);
  color: var(--text-inverse);
  text-decoration: none;
  font-weight: 500;
  font-size: var(--font-size-sm);
  white-space: nowrap;
  transition: all var(--transition-fast);
  border-bottom: 3px solid transparent;
}

.nav-bar a:hover {
  background-color: var(--color-primary-hover);
}

.nav-bar a.active {
  background-color: var(--color-primary-hover);
  border-bottom-color: var(--text-inverse);
}

/* Nav-bar hamburger toggle */
.nav-bar-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-primary);
  border: none;
  cursor: pointer;
  color: var(--text-inverse);
  font-family: inherit;
  font-size: var(--font-size-sm);
  font-weight: 500;
}

.nav-bar-toggle:hover {
  background-color: var(--color-primary-hover);
}

.nav-bar-toggle .hamburger-icon {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 20px;
  height: 16px;
}

.nav-bar-toggle .hamburger-icon span {
  display: block;
  width: 18px;
  height: 2px;
  background-color: var(--text-inverse);
  border-radius: var(--radius-full);
  transition: all var(--transition-normal);
}

.nav-bar-toggle .hamburger-icon span + span {
  margin-top: 4px;
}

.nav-bar-toggle[aria-expanded="true"] .hamburger-icon span:nth-child(1) {
  transform: rotate(45deg) translate(4px, 4px);
}

.nav-bar-toggle[aria-expanded="true"] .hamburger-icon span:nth-child(2) {
  opacity: 0;
}

.nav-bar-toggle[aria-expanded="true"] .hamburger-icon span:nth-child(3) {
  transform: rotate(-45deg) translate(4px, -4px);
}

/* Responsive nav-bar */
@media (max-width: 900px) {
  .nav-bar-toggle {
    display: flex;
  }

  .nav-bar ul {
    display: none;
    flex-direction: column;
    width: 100%;
  }

  .nav-bar ul.nav-bar-open {
    display: flex;
  }

  .nav-bar li {
    width: 100%;
  }

  .nav-bar a {
    width: 100%;
    text-align: center;
    border-bottom: 1px solid var(--color-primary-hover);
  }

  .nav-bar a:last-child {
    border-bottom: none;
  }
}

/* ===== Footer ===== */
.site-footer {
  background-color: var(--bg-primary);
  border-top: 1px solid var(--border-color);
  padding: var(--space-6);
  text-align: center;
  margin-top: auto;
}

.site-footer p {
  margin: 0;
  color: var(--text-muted);
  font-size: var(--font-size-sm);
}

/* ===== Buttons ===== */
button,
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  font-family: inherit;
  font-size: var(--font-size-base);
  font-weight: 500;
  line-height: 1;
  text-decoration: none;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  background-color: var(--color-primary);
  color: var(--text-inverse);
}

button:hover,
.btn:hover {
  background-color: var(--color-primary-hover);
  transform: translateY(-1px);
}

button:active,
.btn:active {
  transform: translateY(0);
}

button:disabled,
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Button Variants */
.btn-primary {
  background-color: var(--color-primary);
  color: var(--text-inverse);
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
}

.btn-secondary {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
}

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

.btn-success {
  background-color: var(--color-success);
  color: var(--text-inverse);
}

.btn-success:hover {
  background-color: var(--color-success-hover);
}

.btn-danger {
  background-color: var(--color-danger);
  color: var(--text-inverse);
}

.btn-danger:hover {
  background-color: var(--color-danger-hover);
}

.btn-warning {
  background-color: var(--color-warning);
  color: var(--text-inverse);
}

.btn-warning:hover {
  background-color: var(--color-warning-hover);
}

.btn-outline {
  background-color: transparent;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
}

.btn-outline:hover {
  background-color: var(--color-primary);
  color: var(--text-inverse);
}

/* Button Sizes */
.btn-sm {
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
}

.btn-lg {
  padding: var(--space-4) var(--space-6);
  font-size: var(--font-size-lg);
}

/* Button Group */
.btn-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  justify-content: center;
}

/* ===== Cards ===== */
.card {
  background-color: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
  border: 1px solid var(--border-color);
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.card-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-6);
  padding: var(--space-4) 0;
}

.card.used {
  opacity: 0.6;
  background-color: var(--bg-tertiary);
}

.card.used::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--text-muted);
}

/* Prompt Card */
.prompt-card {
  background: linear-gradient(135deg, var(--color-primary-light), var(--bg-primary));
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin: var(--space-6) auto;
  max-width: var(--max-width-card);
  text-align: center;
  box-shadow: var(--shadow-md);
}

.prompt-card h2,
.prompt-card p {
  color: var(--text-primary);
  margin-bottom: var(--space-2);
}

/* ===== Forms ===== */
input,
select,
textarea {
  width: 100%;
  max-width: 400px;
  padding: var(--space-3) var(--space-4);
  font-family: inherit;
  font-size: var(--font-size-base);
  line-height: var(--line-height-normal);
  color: var(--text-primary);
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

input:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

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

select {
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
  background-position: right var(--space-3) center;
  background-repeat: no-repeat;
  background-size: 1.5em 1.5em;
  padding-right: var(--space-10);
}

label {
  display: block;
  margin-bottom: var(--space-2);
  font-weight: 500;
  color: var(--text-primary);
}

.form-group {
  margin-bottom: var(--space-4);
}

.form-select {
  margin-left: var(--space-2);
  margin-right: var(--space-4);
}

/* ===== Lists ===== */
ul,
ol {
  max-width: var(--max-width-card);
  margin: var(--space-4) auto;
  padding-left: var(--space-6);
  text-align: left;
}

li {
  margin-bottom: var(--space-2);
  line-height: var(--line-height-relaxed);
  color: var(--text-secondary);
}

/* ===== Text Labels & Status ===== */
.player-turn {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-success);
}

.rule {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-danger);
}

.word-bank {
  font-weight: 600;
  color: var(--color-primary);
}

.error {
  color: var(--color-danger);
  font-weight: 500;
}

.success {
  color: var(--color-success);
  font-weight: 500;
}

/* ===== Utilities ===== */
.text-center {
  text-align: center;
}

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

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

.hidden {
  display: none !important;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

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

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

.flex-wrap {
  flex-wrap: wrap;
}

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

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

/* Spacing Utilities */
.m-0 { margin: 0; }
.m-2 { margin: var(--space-2); }
.m-4 { margin: var(--space-4); }
.mt-2 { margin-top: var(--space-2); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-2 { margin-bottom: var(--space-2); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }
.mx-auto { margin-left: auto; margin-right: auto; }

.p-0 { padding: 0; }
.p-2 { padding: var(--space-2); }
.p-4 { padding: var(--space-4); }
.p-6 { padding: var(--space-6); }

/* Width Utilities */
.w-full { width: 100%; }
.max-w-card { max-width: var(--max-width-card); }
.max-w-content { max-width: var(--max-width-content); }

/* ===== Game-specific shared styles ===== */
.game-container {
  max-width: var(--max-width-content);
  margin: 0 auto;
  padding: var(--space-4);
}

.game-header {
  text-align: center;
  margin-bottom: var(--space-6);
}

.game-controls {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  justify-content: center;
  margin-bottom: var(--space-6);
}

.game-board {
  display: grid;
  gap: var(--space-4);
  margin-bottom: var(--space-6);
}

.score-display {
  background-color: var(--bg-tertiary);
  border-radius: var(--radius-lg);
  padding: var(--space-4) var(--space-6);
  text-align: center;
  font-size: var(--font-size-xl);
  font-weight: 600;
}

.timer {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--color-primary);
  text-align: center;
  padding: var(--space-4);
}

.instructions {
  background-color: var(--bg-tertiary);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin-bottom: var(--space-6);
}

.instructions h2 {
  font-size: var(--font-size-lg);
  margin-bottom: var(--space-3);
}

.instructions p,
.instructions li {
  color: var(--text-secondary);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  :root {
    --header-height: 56px;
  }

  .site-header {
    padding: 0 var(--space-4);
  }

  main {
    padding: var(--space-4) var(--space-3);
  }

  h1 {
    font-size: var(--font-size-2xl);
  }

  .card-container {
    grid-template-columns: 1fr;
  }

  .game-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .game-controls button {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .btn-group {
    flex-direction: column;
  }

  .btn-group button,
  .btn-group .btn {
    width: 100%;
  }
}