:root {
    --board-bg: #bbada0;
    --cell-bg: #cdc1b4;
    --text-dark: #776e65;
    --text-light: #f9f6f2;
    --score-box-bg: #bbada0;
    --button-bg: #8f7a66;
    --button-hover-bg: #a0866c;
    --game-bg: #faf8ef;
    --footer-text-color: #aaaaaa;
    --footer-link-hover-color: #888888;
}

/* 基础样式 */
body {
    font-family: 'Segoe UI', 'Microsoft YaHei', Arial, sans-serif;
    background: var(--game-bg);
    margin: 0;
    padding: 0;
    color: var(--text-dark);
    overflow-x: hidden;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    -webkit-tap-highlight-color: transparent;
    font-size: calc(14px + 0.3vw); /* 基础字体大小自适应 */
}

.game-wrapper {
    width: 100%;
    max-width: min(500px, 90vw);
    margin: 10px auto;
    padding: 0;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* 头部样式 */
.game-header {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-bottom: 20px;
    width: 100%;
}

.header-title-action-mobile-row {
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    width: 100%;
    gap: 10px;
    margin-bottom: 10px;
}

#info-button { 
    grid-column: 1; 
    justify-self: start; 
}

#game-title-text {
    grid-column: 2;
    margin: 0;
    font-size: clamp(1.8em, 5vw, 2.2em); /* 自适应标题大小 */
    color: var(--text-dark);
    font-weight: 900;
    text-align: center;
}

#screenshot-stats-display {
    width: 100%;
    text-align: center;
    font-size: 0.95em;
    color: var(--text-dark);
    margin-top: 10px;
    margin-bottom: 0;
    overflow: hidden;
    max-height: 0;
    opacity: 0;
    transition: max-height 0.3s ease-out, opacity 0.3s ease-out, margin-top 0.3s ease-out;
}

#screenshot-stats-display.visible {
    max-height: 50px;
    opacity: 1;
}

#screenshot-stats-display strong {
    font-weight: bold;
}

/* 分数区域样式 */
.header-scores-container {
    display: flex;
    gap: 5px;
    justify-content: space-around;
    width: 100%;
    min-width: 0;
}

.score-box {
    background: var(--score-box-bg);
    color: var(--text-light);
    padding: 5px 8px;
    border-radius: 3px;
    text-align: center;
    min-width: 100px;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.score-box:hover {
    transform: translateY(-2px);
}

.score-label {
    display: block;
    font-size: 0.85em;
    color: #eee4da;
    text-transform: uppercase;
    margin-bottom: 3px;
    line-height: 1;
    font-weight: bold;
}

.score-value {
    font-size: 1.5em;
    font-weight: bold;
    line-height: 1;
    margin-bottom: 2px;
}

.score-moves-label {
    display: block;
    font-size: 0.7em;
    color: #eee4da;
    line-height: 1;
}

/* 头部按钮样式 */
.header-icon-btn {
    background: transparent;
    border: none;
    color: var(--text-dark);
    font-size: 1.9em;
    padding: 0 5px;
    cursor: pointer;
    line-height: 1;
    flex-shrink: 0;
    min-width: 30px;
    text-align: center;
    transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1), opacity 0.2s ease;
}

.header-icon-btn:hover {
    opacity: 0.7;
    transform: scale(1.1);
}

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

/* 游戏棋盘样式 */
#game-board {
    background: var(--board-bg);
    border-radius: 6px;
    padding: clamp(5px, 1.5vw, 10px);
    width: min(90vw, 450px);
    height: min(90vw, 450px);
    box-sizing: border-box;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(4, 1fr);
    gap: clamp(4px, 1.2vw, 10px);
    touch-action: none;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.15);
    transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    position: relative; /* 为绝对定位的动画元素提供定位上下文 */
}

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

/* 单元格样式 */
.cell {
    background: var(--cell-bg);
    border-radius: 3px;
    font-size: clamp(0.9em, 3.5vw, 2em); /* 自适应单元格字体大小 */
    font-weight: bold;
    color: var(--text-dark);
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    box-sizing: border-box;
    user-select: none;
    transition: background-color 0.1s ease;
    will-change: transform; /* 优化动画性能 */
}

/* 空单元格样式 */
.cell-empty {
    background: var(--cell-bg);
    z-index: 1;
    position: relative;
}

/* 数字单元格样式 */
.cell-number {
    z-index: 2;
    border-radius: 3px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: absolute;
    transition: top 0.16s ease, left 0.16s ease, transform 0.16s ease;
}

/* 不同数值单元格的颜色 */
.cell-2    { background: #eee4da; color: var(--text-dark); }
.cell-4    { background: #ede0c8; color: var(--text-dark); }
.cell-8    { background: #f2b179; color: var(--text-light); }
.cell-16   { background: #f59563; color: var(--text-light); }
.cell-32   { background: #f67c5f; color: var(--text-light); }
.cell-64   { background: #f65e3b; color: var(--text-light); }
.cell-128  { background: #edcf72; color: var(--text-light); }
.cell-256  { background: #edcc61; color: var(--text-light); }
.cell-512  { background: #edc850; color: var(--text-light); }
.cell-1024 { background: #edc53f; color: var(--text-light); }
.cell-2048 { background: #edc22e; color: var(--text-light); }
.cell-4096 { background: #3c3a32; color: var(--text-light); }
.cell-8192 { background: #3c3a32; color: var(--text-light); }

/* 滑动动画 */
.cell-sliding {
    animation: slide 0.2s ease;
    z-index: 2;
}

@keyframes slide {
    0% {
        transform: scale(1);
    }
    100% {
        transform: scale(1);
    }
}

@keyframes moveToMerge {
    0% {
        transform: scale(1);
    }
    100% {
        transform: scale(0.8);
        opacity: 0;
    }
}

/* 合并动画相关样式 */
.cell-merging-active {
    z-index: 3;
    animation: moveToMerge 0.25s ease forwards;
}

.cell-merging-passive {
    z-index: 5;
    animation: receiveMerge 0.25s ease-out;
}

@keyframes receiveMerge {
    0% { transform: scale(1); }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); }
}

/* 新出现的方块动画 */
.cell-new { 
    animation: appear 0.25s ease-out;
}

@keyframes appear {
    0% { transform: scale(0); }
    50% { transform: scale(1.1); }
    100% { transform: scale(1); }
}

/* 弹窗样式 */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.6);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    transition: opacity 0.4s cubic-bezier(0.19, 1, 0.22, 1);
    backdrop-filter: blur(2px);
}

.modal-overlay.active {
    display: flex;
    opacity: 1;
}

.modal-content {
    font-family: 'Segoe UI', 'Microsoft YaHei', Arial, sans-serif;
    background: var(--game-bg);
    padding: 20px 25px;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 8px 25px rgba(0,0,0,0.25);
    color: var(--text-dark);
    transform: scale(0.9);
    transition: transform 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
    max-width: 90%;
    width: auto;
    min-width: 280px;
    position: relative;
}

#info-modal .modal-content {
    max-width: 600px;
}

.modal-overlay.active .modal-content {
    transform: scale(1);
}

.modal-content h2 {
    margin-top: 0;
    margin-bottom: 15px;
    font-size: 1.5em;
    font-weight: bold;
}

.modal-content p {
    font-size: 1.1em;
    margin-bottom: 10px;
    line-height: 1.5;
}

#game-over-modal #modal-steps-score-text {
    font-size: 1.1em;
    margin-bottom: 15px;
    line-height: 1.5;
}

#game-over-modal #modal-feedback-text {
    margin-top: 0;
    margin-bottom: 20px;
}

.modal-feedback {
    font-size: 0.95em;
    color: var(--text-dark);
}

.modal-feedback strong {
    font-weight: bold;
}

/* 弹窗按钮样式 */
#modal-restart-button,
.modal-action-button,
#restart-confirm-yes,
#restart-confirm-no,
#modal-screenshot-button {
    font-family: 'Segoe UI', 'Microsoft YaHei', Arial, sans-serif;
    background: var(--button-bg);
    color: var(--text-light);
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
    padding: 10px 20px;
    font-size: 1em;
    font-weight: bold;
    min-width: 100px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

#modal-restart-button:hover,
.modal-action-button:hover,
#restart-confirm-yes:hover,
#restart-confirm-no:hover,
#modal-screenshot-button:hover {
    background: var(--button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.25);
}

#modal-restart-button:active,
.modal-action-button:active,
#restart-confirm-yes:active,
#restart-confirm-no:active,
#modal-screenshot-button:active {
    transform: translateY(0);
    box-shadow: 0 2px 3px rgba(0, 0, 0, 0.2);
}

#restart-confirm-no {
    background-color: #776e65;
}

#restart-confirm-no:hover {
    background-color: #5e554e;
}

/* 弹窗关闭按钮 */
.modal-close-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    font-size: 1.8em;
    font-weight: bold;
    color: var(--text-dark);
    background: none;
    border: none;
    cursor: pointer;
    line-height: 1;
    padding: 5px;
    transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1), color 0.2s ease;
}

.modal-close-btn:hover {
    color: #333;
    transform: rotate(90deg);
}

/* 信息弹窗内容样式 */
#info-modal-content {
    text-align: left;
    max-height: 60vh;
    overflow-y: auto;
    font-size: 0.9em;
    line-height: 1.6;
    user-select: text;
    -webkit-user-select: text;
    -moz-user-select: text;
    -ms-user-select: text;
}

#info-modal-content strong {
    font-weight: bold;
}

#info-modal-content code {
    background-color: #f0f0f0;
    padding: 0.2em 0.4em;
    border-radius: 3px;
}

#info-modal-content ol,
#info-modal-content ul {
    padding-left: 20px;
}

#info-modal-content br+br {
    display: block;
    margin-bottom: 0.5em;
}

#info-modal-content .secret-message-container br {
    margin-bottom: 0;
}

#info-modal-content a {
    color: var(--text-dark);
    text-decoration: underline;
}

#info-modal-content a:hover {
    color: var(--button-hover-bg);
}

/* 存档/读档区域样式 */
.save-load-section {
    margin-bottom: 15px;
}

.save-load-section h3 {
    font-size: 1.2em;
    margin-bottom: 8px;
}

.save-load-section textarea {
    width: calc(100% - 20px);
    margin-bottom: 10px;
    font-size: 0.9em;
    padding: 8px;
    border-radius: 3px;
    border: 1px solid #ccc;
    resize: vertical;
    box-sizing: border-box;
    user-select: text;
    -webkit-user-select: text;
    -moz-user-select: text;
    -ms-user-select: text;
}

/* 彩带效果 */
.confetti-particle {
    position: fixed;
    pointer-events: none;
    z-index: 9999;
    border-radius: 50%;
}

/* 提示通知样式 */
#toast-notification {
    position: fixed;
    left: 50%;
    top: 25%;
    transform: translate(-50%, -50%);
    padding: 15px 25px;
    border-radius: 8px;
    z-index: 10000;
    text-align: center;
    font-size: 1.1em;
    font-weight: bold;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.4s cubic-bezier(0.19, 1, 0.22, 1), transform 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
    box-shadow: 0 5px 15px rgba(0,0,0,0.3);
}

#toast-notification.success {
    background-color: rgba(0, 0, 0, 0.75);
    color: var(--text-light);
}

#toast-notification.error {
    background-color: rgba(200, 50, 50, 0.85);
    color: var(--text-light);
}

#toast-notification.warning {
    background-color: rgba(230, 160, 0, 0.85);
    color: #333;
}

#toast-notification.info_dark {
    background-color: rgba(20, 20, 20, 0.9);
    color: white;
    font-size: 1em;
    padding: 12px 20px;
}

#toast-notification.visible {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
}

#toast-notification:not(.visible) {
    transform: translate(-50%, -70%) scale(0.95);
}

/* 页脚样式 */
#footer-credit {
    text-align: center;
    padding: 20px 10px;
    font-size: 0.8em;
    color: var(--footer-text-color);
    width: 100%;
    box-sizing: border-box;
}

#footer-credit a {
    color: var(--footer-text-color);
    text-decoration: underline;
}

#footer-credit a:hover {
    color: var(--footer-link-hover-color);
}

/* 游戏结束统计信息样式 */
.game-end-stats {
    text-align: center;
    padding: 10px 15px;
    margin: 10px 0;
    background-color: rgba(238, 228, 218, 0.85);
    border-radius: 6px;
    font-size: 1.1em;
    color: var(--text-dark);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.game-end-stats strong {
    font-weight: bold;
    color: #776e65;
}

/* 响应式布局 */
@media (max-width: 600px) {
    .game-wrapper {
        margin: 5px auto;
        max-width: 95vw;
    }
    
    #game-board {
        padding: clamp(4px, 1.2vw, 6px);
        gap: clamp(3px, 1vw, 6px);
        width: min(95vw, 400px);
        height: min(95vw, 400px);
    }
    
    .modal-content {
        max-width: calc(100% - 30px);
        padding: 15px;
    }
    
    .modal-content h2 {
        font-size: 1.3em;
    }

    .cell {
        font-size: clamp(1.3em, 6vw, 2.2em);
        font-weight: 800;
    }
    
    .header-scores-container {
        flex-wrap: wrap;
        justify-content: center;
        gap: 8px;
    }
    
    .score-box {
        min-width: 80px;
        padding: 4px 6px;
    }
    
    .header-icon-btn {
        font-size: 2.2em;
        padding: 0 8px;
    }
}

@media (max-height: 820px) and (max-width: 600px) {
    .game-wrapper {
        margin: 2px auto;
    }
    
    #game-title-text {
        font-size: clamp(1.8em, 5vw, 2.2em);
    }
    
    .header-scores-container {
        margin-bottom: 5px;
    }
    
    #game-board {
        width: min(90vw, 380px);
        height: min(90vw, 380px);
    }
    
    #footer-credit {
        padding: 10px 5px;
        font-size: 0.7em;
    }
    
    .score-value {
        font-size: clamp(1.2em, 4vw, 1.5em);
    }
    
    .score-moves-label {
        font-size: clamp(0.7em, 2vw, 0.8em);
    }
    
    .cell {
        font-size: clamp(1.2em, 5.5vw, 2em);
    }
}

@media (max-width: 480px) {
    body {
        font-size: calc(14px + 0.4vw);
        padding: 0 5px;
    }
    
    #info-modal-content {
        max-height: 70vh;
    }
    
    .score-box {
        min-width: 85px;
    }
    
    .score-value {
        font-size: clamp(1.2em, 4vw, 1.4em);
    }
    
    .score-moves-label {
        font-size: clamp(0.65em, 2vw, 0.75em);
    }
    
    .header-icon-btn {
        font-size: 2em;
        padding: 0 5px;
    }
    
    .modal-content p {
        font-size: 1.2em;
    }
    
    .modal-action-button {
        font-size: 1.15em;
        padding: 12px 20px;
    }
    
    .cell {
        font-size: clamp(1.1em, 5vw, 1.8em);
    }
}

@media (max-width: 360px) {
    #game-board {
        padding: 3px;
        gap: 3px;
    }
    
    .cell {
        font-size: clamp(1em, 4.5vw, 1.6em);
    }
    
    .score-box {
        min-width: 75px;
        padding: 3px 5px;
    }
}