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

:root {
    --bg-color: #f5f5f5;
    --container-bg: #ffffff;
    --border-color: #e0e0e0;
    --text-color: #333333;
    --text-muted: #666666;
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --add-bg: #d4edda;
    --add-color: #155724;
    --add-line-bg: #e6ffec;
    --delete-bg: #f8d7da;
    --delete-color: #721c24;
    --delete-line-bg: #ffebe9;
    --unchanged-bg: #ffffff;
    --line-num-bg: #f6f8fa;
    --line-num-color: #6e7681;
    --line-num-border: #d0d7de;
    --header-bg: #f6f8fa;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, 'Liberation Mono', Menlo, monospace;
}

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

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 24px;
}

header h1 {
    font-size: 2rem;
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 8px;
}

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

.controls {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    padding: 16px;
    background: var(--container-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 8px;
}

.control-group label {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.control-group.options {
    gap: 16px;
}

.control-group.options label {
    display: flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
}

select {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 0.9rem;
    background: var(--container-bg);
    cursor: pointer;
}

select:focus {
    outline: none;
    border-color: var(--primary-color);
}

input[type="checkbox"] {
    width: 16px;
    height: 16px;
    cursor: pointer;
}

.input-area {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 16px;
}

.input-panel {
    display: flex;
    flex-direction: column;
    background: var(--container-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    background: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    font-weight: 500;
}

.btn-upload {
    padding: 6px 12px;
    font-size: 0.85rem;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-upload:hover {
    background: var(--bg-color);
    border-color: var(--primary-color);
}

.file-input {
    display: none;
}

textarea {
    width: 100%;
    height: 300px;
    padding: 12px;
    border: none;
    font-family: var(--font-mono);
    font-size: 13px;
    line-height: 1.5;
    resize: vertical;
    background: var(--container-bg);
}

textarea:focus {
    outline: none;
}

.action-bar {
    display: flex;
    gap: 12px;
    justify-content: center;
    margin-bottom: 20px;
}

button {
    padding: 10px 24px;
    font-size: 0.95rem;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
    font-weight: 500;
}

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

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

.btn-secondary {
    background: var(--container-bg);
    border: 1px solid var(--border-color);
    color: var(--text-color);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--bg-color);
    border-color: var(--primary-color);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.stats {
    display: flex;
    gap: 24px;
    justify-content: center;
    margin-bottom: 16px;
    font-size: 0.9rem;
}

.stat-item {
    padding: 6px 12px;
    border-radius: 4px;
    font-weight: 500;
}

.stat-item.additions {
    background: var(--add-bg);
    color: var(--add-color);
}

.stat-item.deletions {
    background: var(--delete-bg);
    color: var(--delete-color);
}

.stat-item.unchanged {
    background: var(--line-num-bg);
    color: var(--text-muted);
}

.result-area {
    background: var(--container-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.diff-result {
    overflow-x: auto;
}

/* Side-by-side view */
.diff-table {
    width: 100%;
    border-collapse: collapse;
    font-family: var(--font-mono);
    font-size: 13px;
    table-layout: fixed;
}

.diff-table td {
    padding: 0;
    vertical-align: top;
}

.diff-side {
    width: 50%;
    border-right: 1px solid var(--border-color);
}

.diff-side:last-child {
    border-right: none;
}

.diff-line {
    display: flex;
    min-height: 22px;
    line-height: 22px;
}

.line-num {
    flex-shrink: 0;
    width: 50px;
    padding: 0 8px;
    text-align: right;
    background: var(--line-num-bg);
    color: var(--line-num-color);
    border-right: 1px solid var(--line-num-border);
    user-select: none;
    font-size: 12px;
}

.line-content {
    flex: 1;
    padding: 0 12px;
    white-space: pre;
    overflow-x: auto;
}

.line-add {
    background: var(--add-line-bg);
}

.line-add .line-num {
    background: #ccffd8;
}

.line-add .line-content {
    background: var(--add-line-bg);
}

.line-delete {
    background: var(--delete-line-bg);
}

.line-delete .line-num {
    background: #ffd7d5;
}

.line-delete .line-content {
    background: var(--delete-line-bg);
}

.line-empty {
    background: #f8f8f8;
}

.line-empty .line-num {
    background: #f0f0f0;
}

/* Inline view */
.diff-inline {
    font-family: var(--font-mono);
    font-size: 13px;
}

.diff-inline .diff-line {
    display: flex;
}

.diff-inline .line-num {
    min-width: 40px;
}

.diff-inline .line-num-old,
.diff-inline .line-num-new {
    flex-shrink: 0;
    width: 40px;
    padding: 0 8px;
    text-align: right;
    background: var(--line-num-bg);
    color: var(--line-num-color);
    border-right: 1px solid var(--line-num-border);
    user-select: none;
    font-size: 12px;
    line-height: 22px;
}

.diff-inline .line-marker {
    flex-shrink: 0;
    width: 20px;
    text-align: center;
    font-weight: bold;
    line-height: 22px;
}

.diff-inline .line-add .line-marker {
    color: var(--add-color);
}

.diff-inline .line-delete .line-marker {
    color: var(--delete-color);
}

/* Syntax highlighting overrides */
.line-content code {
    display: block;
    background: transparent !important;
    padding: 0 !important;
    margin: 0 !important;
}

.line-content .hljs {
    background: transparent !important;
    padding: 0 !important;
}

/* Loading */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    padding: 40px;
    color: var(--text-muted);
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.hidden {
    display: none !important;
}

/* Responsive */
@media (max-width: 768px) {
    .input-area {
        grid-template-columns: 1fr;
    }

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

    .control-group {
        justify-content: space-between;
    }

    .action-bar {
        flex-wrap: wrap;
    }

    .diff-table {
        font-size: 12px;
    }

    .line-num {
        width: 40px;
        font-size: 11px;
    }
}

/* Scrollbar styling */
.diff-result::-webkit-scrollbar,
.line-content::-webkit-scrollbar {
    height: 8px;
}

.diff-result::-webkit-scrollbar-track,
.line-content::-webkit-scrollbar-track {
    background: var(--bg-color);
}

.diff-result::-webkit-scrollbar-thumb,
.line-content::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.diff-result::-webkit-scrollbar-thumb:hover,
.line-content::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}