.serial-flex {
    display: flex;
    align-items: stretch;
    margin-top: 1em;
    border: 1px solid #c9ced6;
    border-radius: 4px;
    background: #fff;
    overflow: hidden;
    max-width: 480px;
}

/* エラー時 */
.serial-flex textarea[aria-invalid="true"] {
    outline: none;
}

.serial-flex:has(textarea[aria-invalid="true"]) {
    border: 2px solid #ef1e1e;
}

/* --- 行番号 --- */
.line-numbers {
    flex: 0 0 40px;
    position: relative;
    overflow: hidden;
    border: none;
    border-right: 1px solid #e0e0e0;
    background: #f3f4f6;
    color: #666;
    text-align: right;
    box-sizing: border-box;
    padding-top: var(--pt, 10px);
    padding-bottom: var(--pb, 10px);
}

.line-numbers__inner {
    position: absolute;
    left: 0;
    right: 0;
    top: var(--pt, 10px);
    will-change: transform;
}

.line-numbers__inner div {
    height: var(--lh, 24px);
    line-height: var(--lh, 24px);
    padding: 0 6px;
    margin: 0;
    box-sizing: border-box;
    font-size: var(--fs, 16px);
    font-family: var(--ff, inherit);
}

/* --- textarea --- */
#inquiry_seizoukiban {
    white-space: pre;
    flex: 1;
    min-width: 0;
    border: none !important;
    outline: none;
    resize: vertical;
    line-height: 24px;
    padding: 10px 8px;
    box-sizing: border-box;
}

#serial_error {
    display: none;
    max-width: 480px;
    max-height: 100px;
    overflow-y: auto;
    padding: 8px 10px;
    border: 1px solid #ef1e1e;
    border-radius: 4px;
    background: #fff5f5;
    color: #ef1e1e;
    line-height: 1.6;
}