:root {
    color-scheme: light;
    font-size: 16px;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Sans", Meiryo, sans-serif;
    background-color: #f7f9fc;
    color: #1f2933;
    line-height: 1.6;
}

.page {
    max-width: 960px;
    margin: 0 auto;
    padding: 1.5rem 1rem 3rem;
}

.header {
    margin: 0 auto 1.5rem;
    font-size: 1.2rem;
    text-align: center;
    max-width: 48rem;
    padding: 0 1rem;
}

.content {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    gap: 1.5rem;
    margin: 0 auto 1.75rem;
    width: 100%;
}

.footer {
    margin-top: 2rem;
    text-align: center;
    font-size: 0.875rem;
    color: #52606d;
}

.box {
    width: min(40vw, 220px);
    aspect-ratio: 1 / 1;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(31, 41, 51, 0.12);
    margin: 0 auto;
}

.label {
    text-align: center;
    margin-top: 0.75rem;
    font-size: 0.95rem;
    color: #364152;
}

div#box_ref {
    /* hue: 0-360, saturation: 0-100%, lightness: 0-100% */
    background-color: hsl(0, 75%, 75%);
}

div#box_sample {
    background-color: hsl(180, 75%, 75%);
}

.menu {
    display: grid;
    gap: 1.5rem;
    margin-bottom: 2.5rem;
}

.menu__item {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    padding: 1.5rem;
    border-radius: 18px;
    background: linear-gradient(145deg, #ffffff 0%, #eef2f7 100%);
    box-shadow: 0 20px 30px -15px rgba(15, 23, 42, 0.25);
}

.menu__title {
    font-size: 1.15rem;
    font-weight: 600;
    color: #1f2933;
}

button,
input[type="button"],
.link-button {
    appearance: none;
    border: none;
    border-radius: 999px;
    background: linear-gradient(135deg, #377dff, #274690);
    color: #fff;
    padding: 0.75rem 1.75rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease, background-position 0.2s ease;
    box-shadow: 0 12px 20px rgba(55, 125, 255, 0.25);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
}

button:hover,
input[type="button"]:hover,
.link-button:hover {
    transform: translateY(-1px);
    box-shadow: 0 16px 24px rgba(39, 70, 144, 0.25);
}

button:focus-visible,
input[type="button"]:focus-visible,
.link-button:focus-visible {
    outline: 3px solid rgba(55, 125, 255, 0.7);
    outline-offset: 4px;
}

.updown_btn,
.next_btn,
.start_btn {
    min-width: 160px;
}

input#bar {
    width: min(480px, 100%);
    margin: 0 auto;
}

output#bar_output {
    font-weight: 600;
    color: #1f2933;
}

.download {
    margin-top: 3rem;
}

a {
    color: #274690;
    font-weight: 600;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

@media (min-width: 640px) {
    .menu__item {
        flex-direction: row;
        align-items: center;
        justify-content: space-between;
    }

    .menu__title {
        font-size: 1.25rem;
    }
}

@media (max-width: 768px) {
    .page {
        padding: 1.5rem 1.25rem 2.5rem;
    }

    .box {
        width: min(60vw, 220px);
    }
}

@media (max-width: 600px) {
    .content {
        flex-direction: column;
    }

    .box {
        width: min(80vw, 260px);
    }

    button,
    input[type="button"],
    .link-button {
        width: min(100%, 320px);
    }

    .header {
        font-size: 1.05rem;
    }
}