/* ============================================
   ZOMBIE SURVIVAL - MODERN CSS (2025)
   Best Practices: CSS Variables, Modern Units,
   Performance Optimizations
   ============================================ */

/* ============================================
   CSS CUSTOM PROPERTIES (VARIABLES)
   ============================================ */
:root {
  /* Color Palette */
  --color-primary: #00ff00;
  --color-primary-dark: #00cc00;
  --color-primary-darker: #009900;
  --color-secondary: #0088ff;
  --color-accent: #ffd700;
  --color-accent-orange: #ffaa00;
  --color-danger: #ff0000;
  --color-cyan: #00ffff;

  /* Background Colors */
  --bg-dark: #1a1a1a;
  --bg-darker: #0a0a0a;
  --bg-canvas: #2a2a2a;
  --bg-overlay: rgba(0, 0, 0, 0.7);
  --bg-overlay-dark: rgba(0, 0, 0, 0.9);
  --bg-modal: rgba(10, 10, 30, 0.98);
  --bg-card: rgba(45, 45, 68, 0.8);

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

  /* Safe Area Insets (for notch/Dynamic Island support) */
  --safe-area-top: env(safe-area-inset-top, 0px);
  --safe-area-right: env(safe-area-inset-right, 0px);
  --safe-area-bottom: env(safe-area-inset-bottom, 0px);
  --safe-area-left: env(safe-area-inset-left, 0px);

  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.625rem;
  --radius-xl: 0.9375rem;

  /* Font Sizes (using clamp for responsive) */
  --font-xs: clamp(0.625rem, 0.5rem + 0.5vw, 0.75rem);
  --font-sm: clamp(0.75rem, 0.65rem + 0.5vw, 0.875rem);
  --font-md: clamp(0.875rem, 0.75rem + 0.5vw, 1rem);
  --font-lg: clamp(1rem, 0.85rem + 0.75vw, 1.25rem);
  --font-xl: clamp(1.25rem, 1rem + 1vw, 1.5rem);
  --font-2xl: clamp(1.5rem, 1.2rem + 1.5vw, 2rem);
  --font-3xl: clamp(2rem, 1.5rem + 2vw, 3rem);
  --font-4xl: clamp(2.5rem, 2rem + 2.5vw, 4rem);

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --shadow-glow-primary: 0 0 20px rgba(0, 255, 0, 0.5);
  --shadow-glow-accent: 0 0 20px rgba(255, 215, 0, 0.5);
  --shadow-glow-cyan: 0 0 30px rgba(0, 255, 255, 0.8);

  /* Z-index Scale */
  --z-canvas: 0;
  --z-ui: 10;
  --z-modal: 100;
  --z-overlay: 150;
  --z-tooltip: 200;
  --z-notification: 500;
  --z-nickname: 1000;
}

/* ============================================
   BASE STYLES
   ============================================ */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
    sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  background-color: var(--bg-dark);
  color: #fff;
  overflow: hidden;
  line-height: 1.5;
}

/* ============================================
   GAME CANVAS
   ============================================ */
#gameCanvas {
  display: block;
  background-color: var(--bg-canvas);
  cursor: crosshair;
  position: absolute;
  top: 0;
  left: 0;
  z-index: var(--z-canvas);
}

/* ============================================
   UI CONTAINER
   ============================================ */
#ui {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: var(--z-ui);
  /* Performance optimization */
  contain: layout style;
}

/* ============================================
   STATS PANEL (HUD)
   ============================================ */
#stats {
  position: absolute;
  top: calc(var(--space-lg) + var(--safe-area-top));
  left: calc(var(--space-lg) + var(--safe-area-left));
  /* Fallback for browsers that don't support backdrop-filter */
  background: rgba(0, 0, 0, 0.8);
  padding: var(--space-md);
  border-radius: var(--radius-lg);
  border: 2px solid rgba(0, 255, 0, 0.3);
  pointer-events: auto;
  /* backdrop-filter with -webkit prefix for better support */
  -webkit-backdrop-filter: blur(5px);
  backdrop-filter: blur(5px);
  opacity: 0.9;
}

#player-name-display {
  margin-bottom: var(--space-md);
  font-size: var(--font-lg);
  font-weight: bold;
  color: var(--color-accent);
  text-shadow: 0 0 5px rgba(255, 215, 0, 0.5);
}

/* Health Bar */
#health-container {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

#health-bar {
  width: 12.5rem;
  height: 1.25rem;
  background-color: #333;
  border: 2px solid #fff;
  border-radius: var(--radius-sm);
  overflow: hidden;
}

#health-fill {
  height: 100%;
  width: 100%;
  background: linear-gradient(to right, var(--color-danger), var(--color-primary));
  transition: width var(--transition-base);
  /* GPU acceleration */
  transform: translateZ(0);
}

/* Low health warning */
#health-bar.low-health {
  animation: pulse-health 1s ease-in-out infinite;
  border-color: var(--color-danger);
  box-shadow: 0 0 15px rgba(255, 0, 0, 0.8);
}

#health-bar.low-health #health-fill {
  background: var(--color-danger);
}

/* XP Bar */
#xp-container {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

#xp-bar {
  width: 12.5rem;
  height: 1rem;
  background-color: #333;
  border: 2px solid var(--color-accent);
  border-radius: var(--radius-sm);
  overflow: hidden;
}

#xp-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(to right, #4169E1, var(--color-accent));
  transition: width var(--transition-base);
  box-shadow: 0 0 10px rgba(255, 215, 0, 0.5);
  transform: translateZ(0);
}

/* Near level up indicator */
#xp-bar.near-levelup {
  animation: glow-xp 1.5s ease-in-out infinite;
  border-color: var(--color-accent);
  box-shadow: 0 0 15px rgba(255, 215, 0, 0.8);
}

#xp-bar.near-levelup #xp-fill {
  box-shadow: 0 0 20px rgba(255, 215, 0, 1);
}

#level-text {
  color: var(--color-accent);
  font-weight: bold;
}

#xp-text {
  font-size: var(--font-sm);
  color: var(--color-accent);
  min-width: 3.75rem;
}

/* Stats Info */
#score,
#wave,
#weapon,
#players-online,
#zombies-alive,
#latency-display {
  margin-top: var(--space-xs);
  font-size: var(--font-sm);
}

/* Latency Indicator */
.latency-indicator {
  font-weight: bold;
  font-family: 'Courier New', monospace;
  transition: color 0.3s ease;
}

.latency-indicator.excellent {
  color: #00ff00;
  text-shadow: 0 0 5px rgba(0, 255, 0, 0.5);
}

.latency-indicator.good {
  color: #90ee90;
}

.latency-indicator.fair {
  color: #ffff00;
  text-shadow: 0 0 5px rgba(255, 255, 0, 0.3);
}

.latency-indicator.poor {
  color: #ffa500;
  animation: pulse-warning 1s infinite;
}

.latency-indicator.bad {
  color: #ff0000;
  text-shadow: 0 0 5px rgba(255, 0, 0, 0.5);
  animation: pulse-danger 0.5s infinite;
}

@keyframes pulse-warning {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.7; }
}

@keyframes pulse-danger {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.6; transform: scale(1.1); }
}

#wave {
  color: var(--color-accent-orange);
  font-weight: bold;
}

#weapon {
  color: var(--color-cyan);
}

/* ============================================
   NICKNAME SCREEN
   ============================================ */
#nickname-screen {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  /* Darker fallback for browsers that don't support backdrop-filter */
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: var(--z-nickname);
  pointer-events: auto;
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
}

.nickname-container {
  text-align: center;
  background: linear-gradient(135deg, rgba(26, 26, 26, 0.95) 0%, rgba(42, 42, 42, 0.95) 100%);
  padding: var(--space-2xl) var(--space-2xl);
  border-radius: var(--radius-xl);
  border: 3px solid var(--color-primary);
  box-shadow: var(--shadow-glow-primary);
  max-width: 31.25rem;
  /* Animation performance */
  will-change: transform, opacity;
}

.nickname-container h1 {
  font-size: var(--font-4xl);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
  text-shadow: 0 0 20px rgba(0, 255, 0, 0.8);
  animation: pulse 2s ease-in-out infinite;
}

.nickname-subtitle {
  font-size: var(--font-lg);
  color: #fff;
  margin-bottom: var(--space-xl);
}

#nickname-input {
  width: 100%;
  padding: var(--space-md);
  font-size: var(--font-xl);
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-lg);
  background: rgba(0, 0, 0, 0.5);
  color: #fff;
  text-align: center;
  margin-bottom: var(--space-lg);
  outline: none;
  transition: all var(--transition-base);
}

#nickname-input:focus {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-glow-accent);
}

#start-game-btn {
  width: 100%;
  padding: var(--space-md) var(--space-xl);
  font-size: var(--font-xl);
  font-weight: bold;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: #000;
  border: none;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  text-transform: uppercase;
  /* Performance */
  transform: translateZ(0);
}

#start-game-btn:hover {
  background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary-darker) 100%);
  transform: scale(1.05);
  box-shadow: var(--shadow-glow-primary);
}

#start-game-btn:active {
  transform: scale(0.98);
}

#start-game-btn:disabled {
  background: #666;
  cursor: not-allowed;
  transform: scale(1);
}

.game-info {
  margin-top: var(--space-xl);
  padding-top: var(--space-lg);
  border-top: 1px solid rgba(255, 255, 255, 0.2);
}

.game-info p {
  font-size: var(--font-sm);
  color: #aaa;
  margin: var(--space-sm) 0;
}

/* ============================================
   SPAWN PROTECTION
   ============================================ */
#spawn-protection {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: var(--z-notification);
  pointer-events: none;
}

.protection-message {
  background: rgba(0, 255, 255, 0.9);
  color: #000;
  padding: var(--space-lg) var(--space-2xl);
  border-radius: var(--radius-lg);
  font-size: var(--font-2xl);
  font-weight: bold;
  text-align: center;
  border: 3px solid var(--color-cyan);
  box-shadow: var(--shadow-glow-cyan);
  animation: pulse 1s ease-in-out infinite;
}

/* ============================================
   GAME OVER SCREEN
   ============================================ */
#game-over {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
  /* Fallback for browsers that don't support backdrop-filter */
  background: linear-gradient(135deg, rgba(20, 0, 0, 0.98) 0%, rgba(40, 0, 0, 0.95) 100%);
  padding: var(--space-2xl);
  border-radius: var(--radius-xl);
  border: 3px solid var(--color-danger);
  pointer-events: auto;
  z-index: 9999; /* Au-dessus de tous les widgets addiction */
  -webkit-backdrop-filter: blur(15px);
  backdrop-filter: blur(15px);
  min-width: 350px;
  max-width: 500px;
  box-shadow: 0 0 50px rgba(255, 0, 0, 0.5);
}

.game-over-header h1 {
  color: var(--color-danger);
  font-size: var(--font-4xl);
  margin-bottom: var(--space-sm);
  text-shadow: 0 0 20px var(--color-danger), 0 0 40px rgba(255, 0, 0, 0.5);
  animation: pulse 2s ease-in-out infinite;
}

.game-over-subtitle {
  font-size: var(--font-lg);
  color: #999;
  margin-bottom: var(--space-xl);
  font-style: italic;
}

.game-over-stats {
  background: rgba(0, 0, 0, 0.4);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-xl);
  border: 1px solid rgba(255, 0, 0, 0.3);
}

.stat-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-sm) var(--space-md);
  margin-bottom: var(--space-sm);
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.stat-row:hover {
  background: rgba(255, 255, 255, 0.08);
  transform: translateX(5px);
}

.stat-row:last-child {
  margin-bottom: 0;
}

.stat-row.main-stat {
  background: rgba(255, 215, 0, 0.1);
  border: 2px solid rgba(255, 215, 0, 0.4);
  padding: var(--space-md);
}

.stat-row.main-stat .stat-value {
  font-size: var(--font-2xl);
  color: var(--color-accent);
  text-shadow: 0 0 10px rgba(255, 215, 0, 0.6);
}

.stat-label {
  font-size: var(--font-md);
  color: #ccc;
  font-weight: 500;
}

.stat-value {
  font-size: var(--font-xl);
  color: #fff;
  font-weight: bold;
}

#respawn-btn {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: #000;
  border: none;
  padding: var(--space-md) var(--space-2xl);
  font-size: var(--font-xl);
  font-weight: bold;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  transform: translateZ(0);
  width: 100%;
  box-shadow: 0 5px 15px rgba(0, 255, 0, 0.4);
}

#respawn-btn:hover {
  background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary-darker) 100%);
  transform: translateY(-3px);
  box-shadow: 0 8px 25px rgba(0, 255, 0, 0.6);
}

#respawn-btn:active {
  transform: translateY(-1px);
}

/* ============================================
   WAVE ANNOUNCEMENT
   ============================================ */
#wave-announcement {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
  background: rgba(255, 170, 0, 0.9);
  padding: var(--space-2xl) 5rem;
  border-radius: var(--radius-lg);
  border: 4px solid #ffff00;
  pointer-events: none;
  animation: pulse 0.5s ease-in-out;
}

#wave-announcement h1 {
  color: #fff;
  font-size: clamp(2rem, 3rem + 2vw, 4rem);
  margin-bottom: var(--space-md);
  text-shadow: 0 0 20px #000;
}

#wave-announcement p {
  font-size: var(--font-2xl);
  color: #fff;
  text-shadow: 0 0 10px #000;
}

/* ============================================
   MINIMAP
   ============================================ */
#minimap {
  position: absolute;
  bottom: calc(var(--space-lg) + var(--safe-area-bottom));
  right: calc(var(--space-lg) + var(--safe-area-right));
  width: 12.5rem;
  height: 12.5rem;
  /* Fallback for browsers that don't support backdrop-filter */
  background: rgba(0, 0, 0, 0.85);
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-lg);
  pointer-events: auto;
  -webkit-backdrop-filter: blur(5px);
  backdrop-filter: blur(5px);
  transition: opacity var(--transition-base), transform var(--transition-base);
}

#minimap.hidden-mobile {
  opacity: 0;
  transform: scale(0.5);
  pointer-events: none;
}

/* Minimap Toggle Button */
#minimap-toggle {
  position: absolute;
  bottom: calc(var(--space-lg) + var(--safe-area-bottom));
  right: calc(var(--space-lg) + var(--safe-area-right));
  width: 40px;
  height: 40px;
  background: rgba(0, 255, 0, 0.7);
  border: 2px solid var(--color-primary);
  border-radius: 50%;
  font-size: 20px;
  cursor: pointer;
  pointer-events: auto;
  z-index: 100;
  transition: all var(--transition-base);
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(5px);
  -webkit-backdrop-filter: blur(5px);
  box-shadow: 0 0 15px rgba(0, 255, 0, 0.5);
}

#minimap-toggle:hover {
  transform: scale(1.1);
  box-shadow: 0 0 25px rgba(0, 255, 0, 0.8);
}

#minimap-toggle.active {
  background: rgba(0, 200, 0, 0.9);
  box-shadow: 0 0 30px rgba(0, 255, 0, 1);
}

/* Camera Recenter Button */
#camera-recenter-btn {
  position: absolute;
  bottom: calc(var(--space-lg) + var(--safe-area-bottom) + 50px); /* Above minimap toggle */
  right: calc(var(--space-lg) + var(--safe-area-right));
  width: 40px;
  height: 40px;
  background: rgba(255, 165, 0, 0.7);
  border: 2px solid #ffa500;
  border-radius: 50%;
  font-size: 20px;
  cursor: pointer;
  color: white;
  z-index: 100;
  transition: all var(--transition-base);
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(5px);
  -webkit-backdrop-filter: blur(5px);
  box-shadow: 0 0 15px rgba(255, 165, 0, 0.5);
}

#camera-recenter-btn:hover {
  transform: scale(1.1);
  box-shadow: 0 0 25px rgba(255, 165, 0, 0.8);
  background: rgba(255, 165, 0, 0.9);
}

#camera-recenter-btn:active {
  transform: scale(0.95);
  box-shadow: 0 0 30px rgba(255, 165, 0, 1);
}

/* ============================================
   SHOP
   ============================================ */
#shop {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: min(80%, 50rem);
  max-height: 80vh;
  background: var(--bg-modal);
  border: 4px solid var(--color-accent);
  border-radius: var(--radius-xl);
  pointer-events: auto;
  overflow-y: auto;
  z-index: 9999; /* Au-dessus de tous les widgets addiction */
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}

.shop-header {
  background: linear-gradient(135deg, #1a1a2e, #2d2d44);
  padding: var(--space-lg);
  border-bottom: 3px solid var(--color-accent);
  text-align: center;
  position: sticky;
  top: 0;
  z-index: 10;
}

.shop-header h1 {
  color: var(--color-accent);
  font-size: var(--font-4xl);
  margin-bottom: var(--space-md);
  text-shadow: 0 0 20px var(--color-accent);
}

.shop-header p {
  color: #fff;
  font-size: var(--font-2xl);
  margin: var(--space-md) 0;
}

#shop-close-btn {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #000;
  border: none;
  padding: var(--space-md) var(--space-2xl);
  font-size: var(--font-xl);
  font-weight: bold;
  border-radius: var(--radius-lg);
  cursor: pointer;
  margin-top: var(--space-md);
  transition: all var(--transition-base);
  transform: translateZ(0);
}

#shop-close-btn:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-glow-primary);
}

.shop-content {
  padding: var(--space-lg);
}

.shop-section {
  margin-bottom: var(--space-xl);
}

.shop-section h2 {
  color: var(--color-accent);
  font-size: var(--font-3xl);
  margin-bottom: var(--space-md);
  border-bottom: 2px solid #555;
  padding-bottom: var(--space-md);
}

.shop-item {
  background: var(--bg-card);
  border: 2px solid #555;
  border-radius: var(--radius-lg);
  padding: var(--space-md);
  margin-bottom: var(--space-md);
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: all var(--transition-base);
  transform: translateZ(0);
}

.shop-item:hover {
  border-color: var(--color-accent);
  background: rgba(60, 60, 85, 0.9);
  transform: translateX(5px);
}

.shop-item-info {
  flex: 1;
}

.shop-item-name {
  color: #fff;
  font-size: var(--font-xl);
  font-weight: bold;
  margin-bottom: var(--space-xs);
}

.shop-item-desc {
  color: #aaa;
  font-size: var(--font-sm);
  margin-bottom: var(--space-xs);
}

.shop-item-level {
  color: var(--color-cyan);
  font-size: var(--font-xs);
}

.shop-item-buy {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-xs);
}

.shop-item-price {
  color: var(--color-accent);
  font-size: var(--font-lg);
  font-weight: bold;
}

.shop-buy-btn {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-orange));
  color: #000;
  border: none;
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-md);
  font-weight: bold;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-base);
  transform: translateZ(0);
}

.shop-buy-btn:hover {
  transform: scale(1.1);
  box-shadow: var(--shadow-glow-accent);
}

.shop-buy-btn:disabled {
  background: #444;
  color: #888;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.shop-item.maxed {
  opacity: 0.6;
  border-color: var(--color-primary);
}

.shop-item.maxed .shop-item-name {
  color: var(--color-primary);
}

/* ============================================
   LEVEL UP SCREEN
   ============================================ */
#level-up-screen {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.95);
  z-index: 9999; /* Au-dessus de tous les widgets addiction (max 3000) */
  pointer-events: auto;
  display: flex;
  align-items: center;
  justify-content: center;
  -webkit-backdrop-filter: blur(5px);
  backdrop-filter: blur(5px);
}

.level-up-container {
  text-align: center;
  max-width: 75rem;
  width: 90%;
}

.level-up-title {
  font-size: clamp(2rem, 3rem + 2vw, 4rem);
  color: var(--color-accent);
  text-shadow: 0 0 20px var(--color-accent), 0 0 40px var(--color-accent);
  margin-bottom: var(--space-md);
  animation: pulse 1s infinite;
}

.level-up-subtitle {
  font-size: var(--font-2xl);
  color: #fff;
  margin-bottom: var(--space-2xl);
}

.upgrade-choices {
  display: flex;
  gap: var(--space-xl);
  justify-content: center;
  flex-wrap: wrap;
}

.upgrade-card {
  width: min(100%, 20rem);
  background: rgba(20, 20, 40, 0.95);
  border: 3px solid;
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
  /* Performance */
  will-change: transform;
  transform: translateZ(0);
}

.upgrade-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, transparent 0%, rgba(255, 255, 255, 0.1) 100%);
  opacity: 0;
  transition: opacity var(--transition-base);
}

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

.upgrade-card:hover {
  transform: translateY(-10px) scale(1.05);
  box-shadow: 0 10px 40px rgba(255, 255, 255, 0.3);
}

/* Rarity Styles */
.upgrade-card.common {
  border-color: #9e9e9e;
}

.upgrade-card.common:hover {
  box-shadow: 0 10px 40px rgba(158, 158, 158, 0.5);
}

.upgrade-card.rare {
  border-color: #2196f3;
}

.upgrade-card.rare:hover {
  box-shadow: 0 10px 40px rgba(33, 150, 243, 0.6);
}

.upgrade-card.legendary {
  border-color: var(--color-accent);
  background: rgba(40, 30, 10, 0.95);
}

.upgrade-card.legendary:hover {
  box-shadow: 0 10px 40px rgba(255, 215, 0, 0.8);
}

.upgrade-rarity {
  text-transform: uppercase;
  font-size: var(--font-xs);
  font-weight: bold;
  letter-spacing: 2px;
  margin-bottom: var(--space-md);
}

.upgrade-card.common .upgrade-rarity {
  color: #9e9e9e;
}

.upgrade-card.rare .upgrade-rarity {
  color: #2196f3;
  text-shadow: 0 0 10px #2196f3;
}

.upgrade-card.legendary .upgrade-rarity {
  color: var(--color-accent);
  text-shadow: 0 0 10px var(--color-accent), 0 0 20px var(--color-accent);
  animation: glow 2s infinite;
}

.upgrade-name {
  font-size: var(--font-2xl);
  font-weight: bold;
  color: #fff;
  margin-bottom: var(--space-md);
}

.upgrade-description {
  font-size: var(--font-md);
  color: #ccc;
  line-height: 1.5;
}

/* ============================================
   STATS PANEL
   ============================================ */
#stats-panel {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: min(80%, 56.25rem);
  max-height: 80vh;
  background: var(--bg-modal);
  border: 3px solid var(--color-cyan);
  border-radius: var(--radius-xl);
  pointer-events: auto;
  overflow-y: auto;
  z-index: calc(var(--z-modal) + 20);
  box-shadow: 0 0 40px rgba(0, 255, 255, 0.5);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}

.stats-panel-header {
  background: linear-gradient(135deg, #001a33 0%, #003366 100%);
  padding: var(--space-lg);
  border-bottom: 2px solid var(--color-cyan);
  text-align: center;
}

.stats-panel-header h2 {
  color: var(--color-cyan);
  font-size: var(--font-3xl);
  margin-bottom: var(--space-xs);
  text-shadow: 0 0 10px var(--color-cyan);
}

.stats-hint {
  color: #aaa;
  font-size: var(--font-sm);
  margin: 0;
}

.stats-panel-content {
  padding: var(--space-lg);
}

.stats-section {
  margin-bottom: var(--space-xl);
}

.stats-section h3 {
  color: var(--color-accent);
  font-size: var(--font-xl);
  margin-bottom: var(--space-md);
  border-bottom: 2px solid var(--color-accent);
  padding-bottom: var(--space-sm);
}

.stat-item {
  display: flex;
  justify-content: space-between;
  padding: var(--space-sm) var(--space-md);
  background: rgba(255, 255, 255, 0.05);
  margin-bottom: var(--space-xs);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-primary);
  transition: background var(--transition-fast);
}

.stat-item:hover {
  background: rgba(255, 255, 255, 0.1);
}

.stat-item.rare {
  border-left-color: #2196f3;
}

.stat-item.legendary {
  border-left-color: var(--color-accent);
  background: rgba(255, 215, 0, 0.1);
}

.stat-name {
  color: #fff;
  font-weight: bold;
}

.stat-value {
  color: var(--color-primary);
  font-weight: bold;
}

.stat-value.multiplier {
  color: var(--color-accent-orange);
}

.no-upgrades {
  color: #888;
  font-style: italic;
  text-align: center;
  padding: var(--space-lg);
}

/* ============================================
   INSTRUCTIONS
   ============================================ */
#instructions {
  position: absolute;
  bottom: calc(var(--space-lg) + var(--safe-area-bottom));
  left: calc(var(--space-lg) + var(--safe-area-left));
  /* Fallback for browsers that don't support backdrop-filter */
  background: rgba(0, 0, 0, 0.9);
  padding: var(--space-md);
  border-radius: var(--radius-lg);
  border: 2px solid rgba(0, 136, 255, 0.5);
  pointer-events: auto;
  -webkit-backdrop-filter: blur(15px);
  backdrop-filter: blur(15px);
  box-shadow: 0 0 30px rgba(0, 136, 255, 0.3);
  transition: all var(--transition-base);
  max-width: 280px;
}

#instructions:hover {
  border-color: var(--color-secondary);
  box-shadow: 0 0 40px rgba(0, 136, 255, 0.5);
  background: rgba(0, 0, 0, 0.85);
}

/* Instructions Header */
#instructions-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-sm);
  cursor: pointer;
  padding: var(--space-xs);
  border-radius: var(--radius-md);
  transition: background var(--transition-fast);
}

#instructions-header:hover {
  background: rgba(255, 255, 255, 0.05);
}

#instructions h3 {
  margin: 0;
  color: var(--color-secondary);
  font-size: var(--font-md);
  text-shadow: 0 0 10px rgba(0, 136, 255, 0.5);
  flex: 1;
}

/* Toggle Button */
#instructions-toggle {
  background: rgba(0, 136, 255, 0.2);
  border: 1px solid var(--color-secondary);
  color: var(--color-secondary);
  width: 24px;
  height: 24px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  transition: all var(--transition-fast);
  padding: 0;
  flex-shrink: 0;
}

#instructions-toggle:hover {
  background: rgba(0, 136, 255, 0.4);
  box-shadow: 0 0 10px rgba(0, 136, 255, 0.6);
  transform: scale(1.1);
}

/* Instructions Content */
#instructions-content {
  max-height: 500px;
  overflow: hidden;
  transition: max-height var(--transition-base), opacity var(--transition-base), margin-top var(--transition-base);
  opacity: 1;
  margin-top: var(--space-md);
}

/* Collapsed State */
#instructions.collapsed {
  padding: var(--space-sm);
}

#instructions.collapsed #instructions-content {
  max-height: 0;
  opacity: 0;
  margin-top: 0;
}

#instructions.collapsed #instructions-toggle {
  transform: rotate(-90deg);
}

#instructions.collapsed #instructions-toggle:hover {
  transform: rotate(-90deg) scale(1.1);
}

.control-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-md);
  padding: var(--space-sm);
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.control-item:hover {
  background: rgba(255, 255, 255, 0.08);
  transform: translateX(5px);
}

.control-item:last-child {
  margin-bottom: 0;
}

.control-keys {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  flex-wrap: wrap;
}

.key {
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.15), rgba(255, 255, 255, 0.05));
  color: #fff;
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
  font-size: var(--font-xs);
  font-weight: bold;
  font-family: 'Courier New', monospace;
  border: 1px solid rgba(255, 255, 255, 0.3);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3), inset 0 1px 0 rgba(255, 255, 255, 0.2);
  min-width: 1.5rem;
  text-align: center;
  transition: all var(--transition-fast);
}

.key:hover {
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.25), rgba(255, 255, 255, 0.15));
  border-color: var(--color-secondary);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0, 136, 255, 0.4), inset 0 1px 0 rgba(255, 255, 255, 0.3);
}

.key-icon {
  font-size: var(--font-xl);
  filter: drop-shadow(0 0 5px rgba(255, 255, 255, 0.5));
}

.control-separator {
  color: rgba(255, 255, 255, 0.4);
  font-size: var(--font-xs);
  font-style: italic;
  margin: 0 var(--space-xs);
}

.control-description {
  color: rgba(255, 255, 255, 0.9);
  font-size: var(--font-sm);
  font-weight: 500;
  white-space: nowrap;
}

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes pulse {
  0%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
}

@keyframes glow {
  0%, 100% {
    opacity: 1;
  }
  50% {
    opacity: 0.7;
  }
}

@keyframes pulse-health {
  0%, 100% {
    box-shadow: 0 0 10px rgba(255, 0, 0, 0.6);
  }
  50% {
    box-shadow: 0 0 25px rgba(255, 0, 0, 1), 0 0 40px rgba(255, 0, 0, 0.6);
  }
}

@keyframes glow-xp {
  0%, 100% {
    box-shadow: 0 0 10px rgba(255, 215, 0, 0.6);
  }
  50% {
    box-shadow: 0 0 20px rgba(255, 215, 0, 1), 0 0 35px rgba(255, 215, 0, 0.6);
  }
}

/* ============================================
   RESPONSIVE DESIGN (Mobile-First)
   ============================================ */
@media (max-width: 768px) {
  :root {
    --space-lg: 1rem;
    --space-xl: 1.5rem;
  }

  #stats {
    top: var(--space-sm);
    left: var(--space-sm);
    padding: 0.3rem 0.4rem;
    font-size: 0.65rem;
    background: rgba(0, 0, 0, 0.7);
    opacity: 0.95;
    max-width: 200px;
  }

  #player-name-display {
    font-size: 0.75rem;
    margin-bottom: 0.25rem;
  }

  #health-bar,
  #xp-bar {
    width: 5rem;
    height: 0.625rem;
    border-width: 1px;
  }

  #health-container,
  #xp-container {
    gap: 0.25rem;
    margin-bottom: 0.25rem;
  }

  #health-container span:first-child,
  #xp-container span:first-child {
    font-size: 0.6rem;
    min-width: 20px;
  }

  #health-text,
  #xp-text,
  #level-text {
    font-size: 0.6rem;
    min-width: auto;
  }

  #xp-text {
    min-width: 2.5rem;
  }

  /* Grouper les stats secondaires sur 2 colonnes */
  #stats > div:not(#player-name-display):not(#health-container):not(#xp-container) {
    display: inline-block;
    width: 48%;
    margin-top: 0.2rem;
    font-size: 0.6rem;
    margin-bottom: 0;
  }

  #score {
    margin-right: 2%;
  }

  #wave {
    margin-left: 0;
  }

  #weapon {
    margin-right: 2%;
  }

  #minimap {
    width: 80px;
    height: 80px;
    bottom: 10px;
    right: 10px;
    top: auto;
    transform: none;
    opacity: 0.8;
    border: 3px solid var(--color-primary);
    box-shadow: 0 0 15px rgba(0, 255, 0, 0.4);
    touch-action: none; /* Prevent scrolling when touching minimap */
  }

  #minimap.hidden-mobile {
    transform: scale(0.5);
  }

  #minimap-toggle {
    display: flex !important;
    bottom: 10px;
    right: 10px;
    width: 35px;
    height: 35px;
    font-size: 18px;
  }

  #camera-recenter-btn {
    display: flex !important;
    bottom: 55px; /* Above minimap toggle */
    right: 10px;
    width: 35px;
    height: 35px;
    font-size: 18px;
  }

  .upgrade-choices {
    flex-direction: column;
    align-items: center;
  }

  .nickname-container {
    padding: var(--space-xl);
  }
}

/* ============================================
   TOAST NOTIFICATIONS
   ============================================ */
#toast-container {
  position: fixed;
  top: calc(20px + var(--safe-area-top));
  right: calc(20px + var(--safe-area-right));
  z-index: var(--z-notification);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  pointer-events: none;
  max-width: 350px;
}

.toast {
  background: rgba(20, 20, 40, 0.95);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-md) var(--space-lg);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
  pointer-events: auto;
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  animation: slideInRight 0.3s ease-out;
  display: flex;
  align-items: center;
  gap: var(--space-md);
  transition: all var(--transition-base);
}

.toast.removing {
  animation: slideOutRight 0.3s ease-in;
}

.toast-icon {
  font-size: var(--font-2xl);
  flex-shrink: 0;
}

.toast-content {
  flex: 1;
}

.toast-title {
  font-size: var(--font-md);
  font-weight: bold;
  color: #fff;
  margin-bottom: var(--space-xs);
}

.toast-message {
  font-size: var(--font-sm);
  color: #ccc;
  line-height: 1.4;
}

/* Toast types */
.toast.success {
  border-left-color: var(--color-primary);
}

.toast.info {
  border-left-color: var(--color-secondary);
}

.toast.warning {
  border-left-color: var(--color-accent-orange);
}

.toast.error {
  border-left-color: var(--color-danger);
}

@keyframes slideInRight {
  from {
    transform: translateX(400px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

@keyframes slideOutRight {
  from {
    transform: translateX(0);
    opacity: 1;
  }
  to {
    transform: translateX(400px);
    opacity: 0;
  }
}

/* ============================================
   ACCESSIBILITY
   ============================================ */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Focus styles for accessibility */
*:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* ============================================
   PERFORMANCE OPTIMIZATIONS
   ============================================ */
/* Promote frequently animated elements to their own layer */
#health-fill,
#xp-fill,
#start-game-btn,
#respawn-btn,
.shop-buy-btn {
  will-change: transform;
}

/* Use containment for isolated components */
#shop,
#stats-panel,
#level-up-screen {
  contain: layout style paint;
}

/* ============================================
   MOBILE CONTROLS
   ============================================ */

#mobile-controls {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  pointer-events: none;
  z-index: var(--z-ui);
}

/* Virtual Joystick */
#joystick-container {
  position: absolute;
  bottom: calc(2rem + var(--safe-area-bottom));
  left: calc(2rem + var(--safe-area-left));
  width: 150px;
  height: 150px;
  pointer-events: auto;
}

#joystick-base {
  position: relative;
  width: 150px;
  height: 150px;
  background: radial-gradient(circle, rgba(0, 255, 0, 0.2) 0%, rgba(0, 255, 0, 0.05) 70%, transparent 100%);
  border: 3px solid rgba(0, 255, 0, 0.4);
  border-radius: 50%;
  box-shadow: 0 0 20px rgba(0, 255, 0, 0.3), inset 0 0 20px rgba(0, 255, 0, 0.1);
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
  transition: all 0.3s ease;
}

#joystick-base.active {
  animation: joystick-glow 1s ease-in-out infinite;
  border-color: rgba(0, 255, 0, 0.8);
}

#joystick-stick {
  position: absolute;
  width: 60px;
  height: 60px;
  background: radial-gradient(circle, rgba(0, 255, 0, 0.9) 0%, rgba(0, 255, 0, 0.6) 100%);
  border: 3px solid rgba(0, 255, 0, 1);
  border-radius: 50%;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  box-shadow: 0 0 15px rgba(0, 255, 0, 0.8), inset 0 0 10px rgba(255, 255, 255, 0.3);
  transition: all 0.1s ease-out;
  cursor: pointer;
  /* Performance */
  will-change: transform;
}

#joystick-stick.active {
  animation: stick-pulse 0.8s ease-in-out infinite;
}

/* Auto-shoot button */
#auto-shoot-container {
  position: absolute;
  bottom: calc(2rem + var(--safe-area-bottom));
  right: calc(2rem + var(--safe-area-right));
  pointer-events: auto;
}

#auto-shoot-btn {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(255, 68, 68, 0.85) 0%, rgba(200, 0, 0, 0.85) 100%);
  border: 4px solid rgba(255, 255, 255, 0.7);
  box-shadow: 0 0 25px rgba(255, 68, 68, 0.6), inset 0 0 20px rgba(255, 255, 255, 0.2);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  transition: all 0.2s ease;
  /* Performance */
  will-change: transform;
  transform: translateZ(0);
  -webkit-backdrop-filter: blur(2px);
  backdrop-filter: blur(2px);
}

#auto-shoot-btn:active {
  transform: scale(0.9);
  box-shadow: 0 0 30px rgba(255, 68, 68, 1), inset 0 0 30px rgba(255, 255, 255, 0.4);
}

#auto-shoot-btn.active {
  background: radial-gradient(circle, rgba(255, 215, 0, 0.9) 0%, rgba(255, 140, 0, 0.9) 100%);
  border-color: rgba(255, 215, 0, 1);
  box-shadow: 0 0 35px rgba(255, 215, 0, 1), inset 0 0 20px rgba(255, 255, 255, 0.3);
  animation: pulse-shoot 0.5s ease-in-out infinite;
}

.shoot-icon {
  font-size: 2.5rem;
  filter: drop-shadow(0 0 5px rgba(0, 0, 0, 0.8));
}

.shoot-text {
  font-size: 0.75rem;
  font-weight: bold;
  color: #fff;
  text-shadow: 0 0 5px rgba(0, 0, 0, 0.8);
  letter-spacing: 1px;
}

@keyframes pulse-shoot {
  0%, 100% {
    transform: scale(1);
    box-shadow: 0 0 35px rgba(255, 215, 0, 1), inset 0 0 20px rgba(255, 255, 255, 0.3);
  }
  50% {
    transform: scale(1.05);
    box-shadow: 0 0 50px rgba(255, 215, 0, 1), 0 0 80px rgba(255, 140, 0, 0.6), inset 0 0 30px rgba(255, 255, 255, 0.5);
  }
}

@keyframes joystick-glow {
  0%, 100% {
    box-shadow: 0 0 20px rgba(0, 255, 0, 0.3), inset 0 0 20px rgba(0, 255, 0, 0.1);
  }
  50% {
    box-shadow: 0 0 30px rgba(0, 255, 0, 0.6), 0 0 50px rgba(0, 255, 0, 0.3), inset 0 0 25px rgba(0, 255, 0, 0.2);
  }
}

@keyframes stick-pulse {
  0%, 100% {
    box-shadow: 0 0 15px rgba(0, 255, 0, 0.8), inset 0 0 10px rgba(255, 255, 255, 0.3);
  }
  50% {
    box-shadow: 0 0 25px rgba(0, 255, 0, 1), 0 0 40px rgba(0, 255, 0, 0.6), inset 0 0 15px rgba(255, 255, 255, 0.5);
  }
}

/* Mobile-specific adjustments */
@media (max-width: 768px) {
  #instructions {
    display: none;
  }

  #joystick-container {
    bottom: 0.75rem;
    left: 0.75rem;
    width: 100px;
    height: 100px;
  }

  #joystick-base {
    width: 100px;
    height: 100px;
  }

  #joystick-stick {
    width: 42px;
    height: 42px;
  }

  #auto-shoot-container {
    bottom: 0.75rem;
    right: 0.75rem;
  }

  #auto-shoot-btn {
    width: 85px;
    height: 85px;
  }

  .shoot-icon {
    font-size: 1.75rem;
  }

  .shoot-text {
    font-size: 0.55rem;
  }
}

/* Landscape mode on mobile */
@media (max-width: 768px) and (orientation: landscape) {
  #joystick-container {
    bottom: 0.5rem;
    left: 0.5rem;
    width: 85px;
    height: 85px;
  }

  #joystick-base {
    width: 85px;
    height: 85px;
  }

  #joystick-stick {
    width: 36px;
    height: 36px;
  }

  #auto-shoot-btn {
    width: 70px;
    height: 70px;
  }

  .shoot-icon {
    font-size: 1.4rem;
  }

  .shoot-text {
    font-size: 0.45rem;
  }

  /* IMPROVED: More compact and readable HUD in landscape */
  #stats {
    padding: 0.2rem 0.3rem;
    font-size: 0.6rem;
    background: rgba(0, 0, 0, 0.6);
    border-radius: 0.375rem;
    border-width: 1px;
    max-width: 180px;
  }

  #player-name-display {
    font-size: 0.7rem;
    margin-bottom: 0.2rem;
  }

  #health-bar,
  #xp-bar {
    width: 5rem;
    height: 0.625rem;
  }

  #health-container,
  #xp-container {
    gap: 0.25rem;
    margin-bottom: 0.25rem;
  }

  #health-text,
  #xp-text,
  #level-text {
    font-size: 0.6rem;
    min-width: 2rem;
  }

  #score,
  #wave,
  #weapon,
  #players-online,
  #zombies-alive,
  #latency-display {
    margin-top: 0.15rem;
    font-size: 0.55rem;
    line-height: 1.2;
  }

  /* IMPROVED: Repositionable minimap in landscape */
  #minimap {
    width: 50px;
    height: 50px;
    opacity: 0.7;
    transition: all 0.3s ease, opacity 0.3s ease;
  }

  #minimap:hover {
    opacity: 1;
  }

  /* Make settings button smaller in landscape */
  #settings-btn {
    width: 40px !important;
    height: 40px !important;
    font-size: 20px !important;
    top: 5px !important;
    right: 5px !important;
  }

  #immersive-mode-btn {
    width: 38px !important;
    height: 38px !important;
    font-size: 18px !important;
    top: 50px !important;
    right: 5px !important;
  }

  #fps-counter {
    top: 90px !important;
    right: 5px !important;
    padding: 4px 8px !important;
    font-size: 11px !important;
  }
}

/* IMPROVED: Better visibility in landscape for tablets */
@media (min-width: 769px) and (max-width: 1024px) and (orientation: landscape) {
  #stats {
    padding: 0.375rem 0.5rem;
    font-size: 0.75rem;
  }

  #health-bar,
  #xp-bar {
    width: 8rem;
    height: 0.875rem;
  }

  #minimap {
    width: 80px;
    height: 80px;
  }
}