:root {
    --text-primary: #1d1d1f;
    --text-secondary: rgba(60, 60, 67, 0.65);
    --glass: linear-gradient(135deg, rgba(255, 255, 255, 0.62), rgba(255, 255, 255, 0.35));
    --glass-inset: rgba(255, 255, 255, 0.45);
    --glass-border: rgba(255, 255, 255, 0.65);
    --field-border: rgba(255, 255, 255, 0.7);
    --accent: #0a84ff;
    --accent-soft: rgba(10, 132, 255, 0.25);
    --radius: 28px;
    --shadow: 0 24px 48px -12px rgba(31, 38, 135, 0.18), inset 0 1px 0 rgba(255, 255, 255, 0.75);
}

@media (prefers-color-scheme: dark) {
    :root {
        --text-primary: #f5f5f7;
        --text-secondary: rgba(235, 235, 245, 0.6);
        --glass: linear-gradient(135deg, rgba(50, 55, 70, 0.55), rgba(30, 33, 45, 0.4));
        --glass-inset: rgba(255, 255, 255, 0.08);
        --glass-border: rgba(255, 255, 255, 0.18);
        --field-border: rgba(255, 255, 255, 0.15);
        --accent: #409cff;
        --accent-soft: rgba(64, 156, 255, 0.35);
        --shadow: 0 24px 48px -12px rgba(0, 0, 0, 0.5), inset 0 1px 0 rgba(255, 255, 255, 0.12);
    }
}

* {
    box-sizing: border-box;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    flex-direction: column;
    gap: 20px;
    margin: 0;
    padding: 24px;
    font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Segoe UI', 'Hiragino Sans', sans-serif;
    color: var(--text-primary);
    background: #eef1f7;
}

@media (prefers-color-scheme: dark) {
    body {
        background: #0b0d14;
    }
}

header {
    text-align: center;
}

header h1 {
    font-size: 22px;
    font-weight: 700;
    margin: 0;
    letter-spacing: 0.01em;
}

header p {
    font-size: 13px;
    color: var(--text-secondary);
    margin: 6px 0 0;
}

.card {
    background: var(--glass);
    -webkit-backdrop-filter: blur(30px) saturate(180%);
    backdrop-filter: blur(30px) saturate(180%);
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow);
    padding: 28px 36px;
    width: 440px;
    max-width: 100%;
    border-radius: var(--radius);
}

.card h2 {
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin: 0 0 16px 0;
}

.input-row {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.input-row label {
    font-size: 15px;
    color: var(--text-secondary);
    white-space: nowrap;
}

input[type="number"] {
    font-size: 20px;
    text-align: center;
    flex: 1;
    min-width: 0;
    font-family: inherit;
    padding: 8px 12px;
    border: 1px solid var(--field-border);
    border-radius: 12px;
    background: var(--glass-inset);
    color: var(--text-primary);
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
    -webkit-backdrop-filter: blur(10px);
    backdrop-filter: blur(10px);
}

input[type="number"]:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 4px var(--accent-soft);
}

input[type="button"] {
    font-size: 14px;
    font-weight: 600;
    background: linear-gradient(135deg, rgba(10, 132, 255, 0.92), rgba(64, 156, 255, 0.85));
    color: #fff;
    border: 1px solid rgba(255, 255, 255, 0.35);
    border-radius: 999px;
    padding: 10px 22px;
    cursor: pointer;
    font-family: inherit;
    transition: transform 0.15s, filter 0.2s;
    box-shadow: 0 8px 20px -6px rgba(10, 132, 255, 0.5), inset 0 1px 0 rgba(255, 255, 255, 0.4);
}

input[type="button"]:hover {
    filter: brightness(1.08);
}

input[type="button"]:active {
    transform: scale(0.96);
}

output {
    display: block;
    font-size: 24px;
    font-weight: 600;
    text-align: center;
    min-height: 1.4em;
    margin-top: 18px;
    font-variant-numeric: tabular-nums;
    color: var(--text-primary);
}

footer {
    text-align: center;
    font-size: 13px;
    color: var(--text-secondary);
}

footer a {
    color: var(--accent);
    text-decoration: none;
    font-weight: 600;
}

footer a:hover {
    text-decoration: underline;
}

footer .version {
    margin-top: 6px;
}

@media (max-width: 480px) {
    body {
        padding: 16px 12px;
        gap: 16px;
    }

    header h1 {
        font-size: 18px;
    }

    header p {
        font-size: 12px;
    }

    .card {
        width: 100%;
        padding: 20px 18px;
        border-radius: 22px;
    }

    .input-row label {
        min-width: 100%;
        font-size: 13px;
    }

    input[type="number"] {
        font-size: 18px;
        padding: 10px 12px;
    }

    input[type="button"] {
        padding: 10px 18px;
    }

    output {
        font-size: 20px;
    }
}