* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --diff-line-bg: #e0f2fe;
    --diff-char-highlight: #0369a1;
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Header */
header {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1.5rem 1rem;
    text-align: center;
    box-shadow: var(--shadow);
}

header h1 {
    font-size: 1.8rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* Main */
main {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

/* Controls */
.controls {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    align-items: center;
    margin-bottom: 1.5rem;
    background: var(--card-bg);
    padding: 1rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.btn {
    padding: 0.6rem 1.2rem;
    border: none;
    border-radius: 6px;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

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

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

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

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

.options {
    display: flex;
    gap: 1rem;
    margin-left: auto;
}

.toggle {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.toggle input {
    cursor: pointer;
    width: 16px;
    height: 16px;
}

.icon-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    padding: 0.25rem;
    opacity: 0.6;
    transition: opacity 0.2s;
}

.icon-btn:hover {
    opacity: 1;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-secondary);
    font-size: 0.85rem;
}

/* 统计信息 */
.stats-container {
    display: flex;
    justify-content: center;
    padding: 1rem;
    background: var(--card-bg);
    border-radius: 8px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    margin-top: 1rem;
}

.stats {
    display: flex;
    gap: 2rem;
    font-size: 0.9rem;
}

.stats .added {
    color: var(--diff-char-highlight);
    font-weight: 500;
}

.stats .removed {
    color: var(--diff-char-highlight);
    font-weight: 500;
}

/* Meld 并排模式 */
.meld-container {
    display: grid;
    grid-template-columns: 1fr 40px 1fr;
    gap: 0;
    margin-bottom: 2rem;
    position: relative;
    background: var(--card-bg);
    border-radius: 8px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
    overflow: hidden;
}

.meld-panel {
    display: flex;
    flex-direction: column;
    min-height: 500px;
    background: var(--card-bg);
}

.meld-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
}

.meld-content {
    flex: 1;
    position: relative;
    overflow: hidden;
}

.meld-content textarea {
    position: absolute;
    top: 0;
    left: 0;
    width: calc(100% + 4px);
    height: 100%;
    padding: 16px 16px 16px 16px;
    border: none;
    resize: none;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
    letter-spacing: 0.01em;
    background: transparent;
    color: transparent;
    caret-color: var(--text-primary);
    outline: none;
    z-index: 2;
    white-space: pre;
    overflow-x: auto;
}

.meld-diff {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    padding: 16px;
    pointer-events: none;
    z-index: 1;
    font-family: 'Menlo', 'Monaco', 'Consolas', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
    letter-spacing: 0.01em;
    overflow: hidden;
    color: var(--text-primary);
    white-space: pre;
    overflow-x: auto;
}

.meld-line {
    padding: 0;
    margin: 0;
    min-height: 21px;
    white-space: pre;
}

.meld-line-empty {
    background: rgba(239, 68, 68, 0.1);
}

/* 有差异的行 - 浅蓝色背景 */
.meld-line-changed {
    background: var(--diff-line-bg);
}

/* 字符级差异高亮 - 统一深蓝色 */
.meld-char-added {
    background-color: var(--diff-char-highlight);
    color: white;
    padding: 0;
    border-radius: 0;
}

.meld-char-removed {
    background-color: var(--diff-char-highlight);
    color: white;
    padding: 0;
    border-radius: 0;
}

/* 中间分隔柱 */
.meld-divider {
    background: #f1f5f9;
    border-left: 1px solid var(--border-color);
    border-right: 1px solid var(--border-color);
}

/* Responsive */
@media (max-width: 768px) {
    .meld-container {
        grid-template-columns: 1fr;
        gap: 0;
    }

    .meld-divider {
        display: none;
    }

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

    .options {
        margin-left: 0;
        justify-content: center;
    }
}