:root {
    --bg: #f6f7f9;
    --surface: #ffffff;
    --text: #1f2328;
    --muted: #656d76;
    --border: #d0d7de;
    --focus: #0969da;
    --del-bg: #ffebe9;
    --del-mark: #ffb3ad;
    --del-text: #cf222e;
    --ins-bg: #dafbe1;
    --ins-mark: #8ce0a0;
    --ins-text: #1a7f37;
    --move-bg: #ddf4ff;
    --move-text: #0969da;
    --empty-bg: #f0f1f3;
    --num: #8c959f;
    --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #0d1117;
        --surface: #161b22;
        --text: #e6edf3;
        --muted: #8d96a0;
        --border: #30363d;
        --focus: #4493f8;
        --del-bg: rgba(248, 81, 73, 0.15);
        --del-mark: rgba(248, 81, 73, 0.45);
        --del-text: #ff7b72;
        --ins-bg: rgba(46, 160, 67, 0.15);
        --ins-mark: rgba(46, 160, 67, 0.45);
        --ins-text: #3fb950;
        --move-bg: rgba(56, 139, 253, 0.15);
        --move-text: #58a6ff;
        --empty-bg: #11151b;
        --num: #6e7681;
    }
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
    font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

header, main {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 16px;
}

header {
    display: flex;
    flex-wrap: wrap;
    align-items: baseline;
    gap: 4px 16px;
    padding-top: 20px;
    padding-bottom: 12px;
}

h1 { margin: 0; font-size: 1.4rem; }
.note { margin: 0; color: var(--muted); font-size: 0.875rem; }

.inputs {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.pane { display: flex; flex-direction: column; gap: 6px; min-width: 0; }
.pane-title { font-weight: 600; }
.pane-title small { color: var(--muted); font-weight: 400; margin-left: 4px; }

textarea {
    width: 100%;
    min-height: 220px;
    resize: vertical;
    padding: 10px 12px;
    background: var(--surface);
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: 8px;
    font: 13px/1.5 var(--mono);
    tab-size: 4;
}

textarea:focus { outline: 2px solid var(--focus); outline-offset: -1px; border-color: transparent; }

.toolbar {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    gap: 8px;
    margin: 16px 0 10px;
    min-height: 32px;
}

.stats { display: flex; flex-wrap: wrap; gap: 12px; font-size: 0.875rem; font-weight: 600; }
.stat-del { color: var(--del-text); }
.stat-ins { color: var(--ins-text); }
.stat-mov { color: var(--move-text); }
.stat-chg, .same-badge { color: var(--muted); }

.actions { display: flex; gap: 8px; }

button {
    padding: 5px 14px;
    background: var(--surface);
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: 6px;
    font: inherit;
    font-size: 0.875rem;
    cursor: pointer;
}

button:hover { border-color: var(--muted); }
button:focus-visible { outline: 2px solid var(--focus); outline-offset: 1px; }

.result {
    margin-bottom: 32px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
}

.placeholder { margin: 0; padding: 24px; color: var(--muted); text-align: center; }

.grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    font: 13px/1.5 var(--mono);
    tab-size: 4;
}

.line {
    display: grid;
    grid-template-columns: 3.5em 1fr;
    min-width: 0;
}

.line:nth-child(odd) { border-right: 1px solid var(--border); }
.line.del .num { color: var(--del-text); }
.line.ins .num { color: var(--ins-text); }
.line.moved .num { color: var(--move-text); }

.num {
    padding: 0 8px;
    color: var(--num);
    text-align: right;
    user-select: none;
}

.code {
    padding: 0 10px;
    white-space: pre-wrap;
    overflow-wrap: anywhere;
    min-height: 1.5em;
}

.del { background: var(--del-bg); }
.ins { background: var(--ins-bg); }
.moved { background: var(--move-bg); }
.empty { background: var(--empty-bg); }

.move-tag {
    margin-left: 12px;
    color: var(--move-text);
    font: 11px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    user-select: none;
}

.del-mark { background: var(--del-mark); border-radius: 2px; }
.ins-mark { background: var(--ins-mark); border-radius: 2px; }

@media (max-width: 720px) {
    .inputs { grid-template-columns: 1fr; }
    textarea { min-height: 160px; }
    .grid { font-size: 12px; }
    .line { grid-template-columns: 2.5em 1fr; }
    .num { padding: 0 4px; }
    .code { padding: 0 6px; }
}