/* ===== 基础重置 & 全局样式 ===== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --bg: #f5f5f7;
    --card-bg: #ffffff;
    --text: #1d1d1f;
    --text-secondary: #6e6e73;
    --border: #d2d2d7;
    --primary: #0071e3;
    --primary-hover: #0077ed;
    --delete-bg: #ffe0e0;
    --delete-text: #c41e3a;
    --insert-bg: #d9f9e0;
    --insert-text: #1a7f3a;
    --replace-bg: #fff3cd;
    --replace-text: #856404;
    --radius: 10px;
    --shadow: 0 2px 12px rgba(0,0,0,0.06);
    --transition: 0.2s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
        "Microsoft YaHei", "Helvetica Neue", sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
}

/* ===== 头部 ===== */
.header {
    text-align: center;
    padding: 28px 20px 12px;
}
.header h1 {
    font-size: 24px;
    font-weight: 600;
    letter-spacing: -0.3px;
}
.header .subtitle {
    font-size: 13px;
    color: var(--text-secondary);
    margin-top: 4px;
}
.logout-btn {
    position: absolute;
    top: 12px;
    right: 20px;
    font-size: 13px;
    color: var(--text-secondary);
    cursor: pointer;
    text-decoration: none;
    padding: 4px 10px;
    border-radius: 6px;
    transition: color .2s, background .2s;
}
.logout-btn:hover {
    color: var(--delete-text);
    background: #f5f5f5;
}
.header { position: relative; }

/* ===== 上传区域 ===== */
.upload-section {
    display: flex;
    gap: 16px;
    max-width: 900px;
    margin: 0 auto;
    padding: 0 20px;
    align-items: center;
}

.upload-card {
    flex: 1;
    background: var(--card-bg);
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 32px 20px;
    text-align: center;
    cursor: pointer;
    transition: border-color var(--transition), box-shadow var(--transition);
    position: relative;
    min-height: 160px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.upload-card:hover,
.upload-card.drag-over {
    border-color: var(--primary);
    box-shadow: var(--shadow);
}
.upload-card.has-file {
    border-style: solid;
    border-color: var(--border);
}
.upload-card .icon {
    font-size: 36px;
    margin-bottom: 10px;
}
.upload-card .hint {
    font-size: 14px;
    color: var(--text-secondary);
}
.upload-card .hint strong {
    color: var(--primary);
    cursor: pointer;
}
.upload-card .file-name {
    font-size: 14px;
    font-weight: 500;
    margin-top: 8px;
    word-break: break-all;
}
.upload-card .file-meta {
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 4px;
}
.upload-card .remove-btn {
    position: absolute;
    top: 10px;
    right: 12px;
    background: none;
    border: none;
    font-size: 18px;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 2px 6px;
    border-radius: 4px;
    transition: color var(--transition);
}
.upload-card .remove-btn:hover {
    color: var(--delete-text);
}

input[type="file"] {
    display: none;
}

.vs-divider {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-secondary);
    flex-shrink: 0;
}

/* ===== 对比按钮 ===== */
.action-row {
    text-align: center;
    margin: 20px 0;
}
.btn-compare {
    padding: 10px 48px;
    font-size: 15px;
    font-weight: 500;
    color: #fff;
    background: var(--primary);
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: background var(--transition), transform var(--transition);
}
.btn-compare:hover {
    background: var(--primary-hover);
}
.btn-compare:active {
    transform: scale(0.97);
}
.btn-compare:disabled {
    background: #a0c4e8;
    cursor: not-allowed;
}

/* ===== 导出按钮 ===== */
.export-row {
    text-align: center;
    margin-bottom: 12px;
    display: none;
}
.export-row.show {
    display: block;
}
.btn-export {
    padding: 7px 28px;
    font-size: 13px;
    font-weight: 500;
    color: var(--primary);
    background: #fff;
    border: 1px solid var(--primary);
    border-radius: var(--radius);
    cursor: pointer;
    transition: background var(--transition);
}
.btn-export:hover {
    background: #e8f0fe;
}
.btn-export:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* ===== 统计栏 ===== */
.stats-bar {
    display: flex;
    justify-content: center;
    gap: 24px;
    margin: 0 auto 16px;
    max-width: 900px;
    padding: 0 20px;
    font-size: 13px;
    color: var(--text-secondary);
}
.stats-bar .stat {
    display: flex;
    align-items: center;
    gap: 5px;
}
.stats-bar .stat .dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    display: inline-block;
}
.dot.delete { background: var(--delete-text); }
.dot.insert { background: var(--insert-text); }
.dot.modify { background: var(--replace-text); }
.dot.equal { background: #aaa; }

/* ===== 结果区域 ===== */
.result-section {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px 40px;
    display: none; /* 默认隐藏，有结果后显示 */
}
.result-section.show {
    display: flex;
    flex-direction: column;
}

.diff-panels {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    background: var(--card-bg);
    box-shadow: var(--shadow);
}

.panel-header {
    background: #fafafa;
    padding: 10px 16px;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
    text-align: center;
    text-overflow: ellipsis;
    overflow: hidden;
    white-space: nowrap;
}
.panel-header.left-header {
    border-right: 1px solid var(--border);
}

.panel-content {
    padding: 10px 14px;
    max-height: 60vh;
    overflow-y: auto;
    font-size: 14px;
    line-height: 1.8;
}
.left-content {
    border-right: 1px solid var(--border);
}

.diff-row {
    display: flex;
    align-items: flex-start;
    min-height: 1.8em;
    border-radius: 3px;
    padding: 2px 6px;
    margin-bottom: 2px;
    transition: background 0.15s;
}
.diff-row .row-num {
    flex-shrink: 0;
    width: 32px;
    font-size: 11px;
    color: #999;
    text-align: right;
    margin-right: 8px;
    user-select: none;
}
.diff-row .row-text {
    flex: 1;
    word-break: break-word;
}

.diff-row.equal {
    background: transparent;
}
.diff-row.delete {
    background: var(--delete-bg);
}
.diff-row.delete .row-text {
    color: var(--delete-text);
    text-decoration: line-through;
}
.diff-row.insert {
    background: var(--insert-bg);
}
.diff-row.insert .row-text {
    color: var(--insert-text);
}
.diff-row.replace {
    background: transparent;  /* 不再整段标黄，用行内 diff */
}
.diff-row.empty {
    background: #f0f0f0;
}

/* ===== 行内逐字 diff ===== */
.inline-diff {
    line-height: 1.9;
}
.inline-equal {
    color: var(--text);
}
.inline-delete {
    background: #fbb6c0;
    color: #a31d2f;
    text-decoration: line-through;
    border-radius: 2px;
    padding: 1px 1px;
}
.inline-insert {
    background: #a3e4b8;
    color: #1a5c2e;
    border-radius: 2px;
    padding: 1px 1px;
}
.inline-empty {
    color: #999;
    font-style: italic;
}

/* 同步滚动锁定提示 */
.sync-indicator {
    display: none;
    text-align: center;
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 8px;
}

/* ===== 空状态 / 加载 ===== */
.loading {
    text-align: center;
    padding: 40px;
    color: var(--text-secondary);
    font-size: 14px;
    display: none;
}
.loading.show {
    display: block;
}

.empty-section {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
    font-size: 14px;
    display: none;
}
.empty-section.show {
    display: block;
}

/* ===== 响应式：小屏幕栈叠 ===== */
@media (max-width: 720px) {
    .upload-section {
        flex-direction: column;
    }
    .vs-divider {
        transform: rotate(90deg);
    }
    .diff-panels {
        grid-template-columns: 1fr;
    }
    .left-content {
        border-right: none;
        border-bottom: 1px solid var(--border);
    }
    .panel-header.left-header {
        border-right: none;
    }
}