:root {
    --bg: #f5f5f5;
    --surface: #ffffff;
    --border: #e0e0e0;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --accent: #4f7ef8;
    --accent-hover: #3a6ae0;
    --radius: 12px;
    --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

* {
    box-sizing: border-box;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    flex-direction: column;
    margin: 0;
    padding: 24px;
    background: var(--bg);
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    color: var(--text-primary);
}

h5 {
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin: 0 0 20px 0;
}

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
    padding: 28px 36px;
    width: 480px;
    max-width: 100%;
    border-radius: var(--radius);
}

.section {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
    margin-bottom: 16px;
}

.section-label {
    font-size: 14px;
    color: var(--text-secondary);
    white-space: nowrap;
    min-width: 60px;
}

select {
    font-size: 16px;
    padding: 8px 10px;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    background: var(--bg);
    color: var(--text-primary);
    outline: none;
    cursor: pointer;
    transition: border-color 0.2s;
    font-family: inherit;
}

select:focus {
    border-color: var(--accent);
}

input[type="text"],
input[type="number"] {
    font-size: 18px;
    padding: 8px 12px;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    background: var(--bg);
    color: var(--text-primary);
    outline: none;
    transition: border-color 0.2s;
    font-family: inherit;
    flex: 1;
    min-width: 0;
}

input[type="text"]:focus,
input[type="number"]:focus {
    border-color: var(--accent);
}

input[type="number"]:disabled,
input[type="text"]:disabled {
    color: var(--text-secondary);
    cursor: default;
}

input#cstsys,
input#cstosys {
    width: 6ch;
    flex: none;
    font-size: 16px;
    text-align: center;
}

.arrow-btn {
    display: flex;
    justify-content: center;
    margin: 4px 0 16px;
}

.arrow-btn button {
    font-size: 14px;
    font-weight: 600;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: 8px;
    padding: 9px 28px;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
}

.arrow-btn button:hover {
    background: var(--accent-hover);
}

.arrow-btn button:active {
    transform: scale(0.96);
}

.mid-section {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 16px;
}

.divider {
    height: 1px;
    background: var(--border);
    margin: 20px 0;
}