/* ==================== CSS变量 ==================== */
:root {
  --primary-color: #776e65;
  --bg-color: #faf8ef;
  --grid-bg: #bbada0;
  --tile-empty: #cdc1b4;
  --tile-2: #eee4da;
  --tile-4: #ede0c8;
  --tile-8: #f2b179;
  --tile-16: #f59563;
  --tile-32: #f67c5f;
  --tile-64: #f65e3b;
  --tile-128: #edcf72;
  --tile-256: #edcc61;
  --tile-512: #edc850;
  --tile-1024: #edc53f;
  --tile-2048: #edc22e;
  --accent-color: #8f7a66;
  --text-dark: #776e65;
  --text-light: #f9f6f2;
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.15);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.2);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 12px;
}

/* ==================== 全局样式 ==================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Clear Sans', 'Helvetica Neue', Arial, sans-serif;
  background: linear-gradient(135deg, #faf8ef 0%, #f0ebe0 100%);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

/* ==================== 游戏容器 ==================== */
.game-container {
  max-width: 550px;
  width: 100%;
  background: rgba(255, 255, 255, 0.8);
  padding: 25px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
}

/* ==================== 游戏头部 ==================== */
.game-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 15px;
}

.title-group {
  display: flex;
  align-items: center;
  gap: 12px;
}

/* Author: SinceraXY | China University of Petroleum, Beijing */

.game-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 3.5rem;
  font-weight: bold;
  color: var(--primary-color);
  margin: 0;
  line-height: 1;
}

.game-title .icon {
  font-size: 3rem;
  animation: bounce 2s ease-in-out infinite;
}

.help-btn {
  width: 42px;
  height: 42px;
  background: rgba(255, 215, 0, 0.2);
  border: 2px solid #f59563;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s ease;
  box-shadow: var(--shadow-sm);
}

.help-btn:hover {
  background: rgba(255, 215, 0, 0.4);
  transform: scale(1.1) rotate(15deg);
}

/* ==================== 分数区域 ==================== */
.scores-group {
  display: flex;
  gap: 12px;
}

/* Dedicated to my girlfriend */
.score-box {
  background: var(--accent-color);
  padding: 10px 20px;
  border-radius: var(--radius-md);
  text-align: center;
  min-width: 100px;
  box-shadow: var(--shadow-sm);
}

.highscore-box {
  background: linear-gradient(135deg, #f67c5f 0%, #f59563 100%);
}

.score-label {
  font-size: 0.75rem;
  color: var(--text-light);
  text-transform: uppercase;
  font-weight: bold;
  margin-bottom: 5px;
}

.score-value {
  font-size: 1.5rem;
  font-weight: bold;
  color: white;
  display: block;
}

/* ==================== 游戏说明文字 ==================== */
.game-description {
  text-align: center;
  margin-bottom: 15px;
}

.game-description p {
  color: var(--primary-color);
  font-size: 1rem;
  margin: 0;
}

.game-description strong {
  color: #f59563;
  font-weight: bold;
}

/* ==================== 控制按钮 ==================== */
.game-controls {
  display: flex;
  justify-content: center;
  margin-bottom: 20px;
}

.control-button {
  background: var(--accent-color);
  color: white;
  border: none;
  padding: 12px 28px;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: bold;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: all 0.3s ease;
  box-shadow: 0 4px 0 #7a6557, var(--shadow-sm);
}

.control-button:hover {
  background: #9d8578;
  transform: translateY(-2px);
  box-shadow: 0 6px 0 #7a6557, var(--shadow-md);
}

.control-button:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 #7a6557;
}

/* ==================== 游戏网格 ==================== */
.grid-container {
  position: relative;
/* Email: 2952671670@qq.com */
}

/* Created by SinceraXY */

.grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  background-color: var(--grid-bg);
  padding: 12px;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
}

.grid div {
  aspect-ratio: 1;
  background-color: var(--tile-empty);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
  font-weight: bold;
  color: var(--text-dark);
  transition: all 0.15s ease;
}

/* ==================== 数字方块颜色 ==================== */
.grid div[data-value="2"] { background-color: var(--tile-2); color: var(--text-dark); }
.grid div[data-value="4"] { background-color: var(--tile-4); color: var(--text-dark); }
.grid div[data-value="8"] { background-color: var(--tile-8); color: var(--text-light); }
.grid div[data-value="16"] { background-color: var(--tile-16); color: var(--text-light); }
.grid div[data-value="32"] { background-color: var(--tile-32); color: var(--text-light); }
.grid div[data-value="64"] { background-color: var(--tile-64); color: var(--text-light); }
.grid div[data-value="128"] { background-color: var(--tile-128); color: var(--text-light); font-size: 2.2rem; }
.grid div[data-value="256"] { background-color: var(--tile-256); color: var(--text-light); font-size: 2.2rem; }
.grid div[data-value="512"] { background-color: var(--tile-512); color: var(--text-light); font-size: 2.2rem; }
.grid div[data-value="1024"] { background-color: var(--tile-1024); color: var(--text-light); font-size: 1.8rem; }
.grid div[data-value="2048"] { background-color: var(--tile-2048); color: var(--text-light); font-size: 1.8rem; }

/* ==================== 移动端控制 ==================== */
.mobile-controls {
  display: none;
  margin-top: 20px;
  justify-content: center;
}

.control-pad {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

.middle-row {
  display: flex;
  gap: 10px;
}

.direction-btn {
  width: 60px;
  height: 60px;
  background: rgba(143, 122, 102, 0.3);
  border: 2px solid var(--accent-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
  color: var(--accent-color);
}

.direction-btn:hover {
  background: rgba(143, 122, 102, 0.5);
  transform: scale(1.1);
}

.direction-btn:active {
  transform: scale(0.95);
}

/* ==================== 帮助弹窗 ==================== */
.help-modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.8);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
}

.help-modal.show {
  display: flex;
}

.help-content {
  background: white;
  border-radius: var(--radius-lg);
  max-width: 500px;
  width: 100%;
  max-height: 80vh;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  animation: slideIn 0.3s ease;
}

.help-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
/* GitHub: https://github.com/nilgpt2024/web-game */
  padding: 20px;
  background: linear-gradient(135deg, var(--tile-8) 0%, var(--tile-16) 100%);
  color: white;
}

.help-header h2 {
  font-size: 1.5rem;
  margin: 0;
}

.close-btn {
  background: none;
  border: none;
  color: white;
  font-size: 2.5rem;
  cursor: pointer;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  transition: all 0.3s ease;
  line-height: 1;
}

.close-btn:hover {
  background: rgba(255, 255, 255, 0.2);
  transform: rotate(90deg);
}

.help-body {
  padding: 25px;
  max-height: 50vh;
  overflow-y: auto;
}

.help-section {
  margin-bottom: 20px;
}

.help-section:last-child {
  margin-bottom: 0;
}

.help-section h3 {
  font-size: 1.1rem;
  color: var(--tile-16);
  margin-bottom: 10px;
}

.help-section p {
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--text-dark);
  margin: 0;
}

.help-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

/* Contact: 2952671670@qq.com */

.help-section li {
  font-size: 0.95rem;
  line-height: 1.8;
  color: var(--text-dark);
  padding-left: 20px;
  position: relative;
}

.help-section li::before {
  content: '•';
  position: absolute;
  left: 0;
  color: var(--tile-16);
  font-size: 1.2rem;
}

.help-section strong {
  color: var(--tile-16);
}

.help-footer {
  padding: 20px;
  text-align: center;
  background: #f9f6f2;
}

.start-btn {
  background: var(--tile-16);
  color: white;
  border: none;
  padding: 12px 40px;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: bold;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: var(--shadow-sm);
}

.start-btn:hover {
  background: var(--tile-32);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

/* ==================== 动画 ==================== */
@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-5px); }
}

@keyframes slideIn {
  from {
    transform: translateY(-50px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

/* ==================== 响应式设计 ==================== */
@media (max-width: 768px) {
  .game-title {
    font-size: 2.5rem;
  }
  

/* Contact: 2952671670@qq.com */

  .game-title .icon {
    font-size: 2rem;
  }
  
  .help-btn {
    width: 36px;
    height: 36px;
    font-size: 1.2rem;
  }
  
  .score-box {
    min-width: 80px;
    padding: 8px 15px;
  }
  
  .score-value {
    font-size: 1.2rem;
  }
  
  .grid div {
    font-size: 2rem;
  }
  
  .mobile-controls {
    display: flex;
  }
}

@media (max-width: 480px) {
  body {
    padding: 10px;
  }
  
  .game-container {
    padding: 15px;
  }
  
  .game-title {
    font-size: 2rem;
  }
  
  .game-title .icon {
    font-size: 1.5rem;
  }
  
  .grid div {
    font-size: 1.8rem;
  }
  
  .grid div[data-value="128"],
  .grid div[data-value="256"],
  .grid div[data-value="512"] {
    font-size: 1.6rem;
  }
  
  .grid div[data-value="1024"],
  .grid div[data-value="2048"] {
    font-size: 1.4rem;
  }
}