@import url('https://fonts.googleapis.com/css2?family=Kiwi+Maru&display=swap');

/* 全体設定 */
:root {
    --bg1: #1d3360;
    --bg2: #12213d;
    --bg3: #070d1a;
    --text: #eef2ff;
    --sub: #c0cae0;
    --line: rgba(255, 255, 255, .12);
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    min-height: 100vh;
    color: var(--text);
    font-family: "Kiwi Maru", serif;

    background:
        radial-gradient(circle at 20% 20%, rgba(255, 255, 255, .15) 1px, transparent 1px),
        radial-gradient(circle at 70% 30%, rgba(255, 255, 255, .12) 1px, transparent 1px),
        radial-gradient(circle at 85% 75%, rgba(255, 255, 255, .15) 1px, transparent 1px),
        radial-gradient(circle at 40% 80%, rgba(255, 255, 255, .12) 1px, transparent 1px),
        linear-gradient(180deg, var(--bg1), var(--bg2), var(--bg3));

    background-size:
        260px 260px,
        320px 320px,
        220px 220px,
        180px 180px,
        auto;
}

.top-nav a,
h2,
.box p,
footer {
    color: var(--sub);
}

/* デフォルト */
main {
    max-width: 900px;
    margin: auto;
    padding: 100px 32px;
    position: relative;
    z-index: 1;
}

header {
    margin-bottom: 50px;
}

h1 {
    margin: 0;
    font-size: clamp(2rem, 5vw, 3em);
    font-weight: 300;
}

h2 {
    margin-bottom: 20px;
    font-size: .9rem;
    letter-spacing: .15em;
}

a {
    color: var(--text);
    text-decoration: none;
    border: 1px solid transparent;
}

section {
    margin-top: 40px;
}

footer {
    margin-top: 100px;
    font-size: .85rem;
}

/* ボタン */
button {
    padding: 10px 20px;

    color: var(--text);

    border: 1px solid var(--line);
    border-radius: 10px;

    background: rgba(255, 255, 255, .10);

    transition:
        background .2s ease,
        border-color .2s ease,
        transform .2s ease;

    cursor: pointer;
}

button:hover {
    background: rgba(255, 255, 255, .08);
    border-color: rgba(255, 255, 255, .2);
    transform: translateY(-1px);
}

button:active {
    transform: translateY(0);
}

/* テキストエリア */
textarea {
    width: 100%;
    min-height: 180px;

    padding: 16px;

    color: var(--text);
    font: inherit;

    border: 1px solid var(--line);
    border-radius: 12px;

    background: rgba(255, 255, 255, .04);

    resize: vertical;
    outline: none;

    transition:
        border-color .2s ease,
        background .2s ease;
}

textarea::placeholder {
    color: var(--sub);
}

textarea:hover {
    background: rgba(255, 255, 255, .06);
}

textarea:focus {
    border-color: rgba(255, 255, 255, .25);
    background: rgba(255, 255, 255, .07);
}

input[type="text"],
input[type="number"],
input[type="email"],
input[type="password"],
input[type="search"],
select {
    width: 100%;
    margin-bottom: 12px;
    padding: 12px 16px;
    color: var(--text);
    font: inherit;
    border: 1px solid var(--line);
    border-radius: 12px;
    background: rgba(255, 255, 255, .04);
    outline: none;
    transition:
        border-color .2s ease,
        background .2s ease;
}

input[type="text"],
input[type="number"],
input[type="email"],
input[type="password"],
input[type="search"],
select::placeholder {
    color: var(--sub);
}

input[type="text"],
input[type="number"],
input[type="email"],
input[type="password"],
input[type="search"],
select:hover {
    background: rgba(255, 255, 255, .06);
}

input[type="text"],
input[type="number"],
input[type="email"],
input[type="password"],
input[type="search"],
select:focus {
    border-color: rgba(255, 255, 255, .25);
    background: rgba(255, 255, 255, .07);
}

input[type="file"] {
    width: 100%;
    padding: 12px;
    color: var(--sub);
    border: 1px dashed var(--line);
    border-radius: 12px;
    background: rgba(255, 255, 255, .04);
}

input[type="file"]::file-selector-button {
    margin-right: 12px;
    padding: 8px 14px;
    color: var(--text);
    border: 1px solid var(--line);
    border-radius: 8px;
    background: rgba(255, 255, 255, .08);
    cursor: pointer;
}

/* アコーディオン */
details {
    margin-bottom: 12px;
    border: 1px solid var(--line);
    border-radius: 14px;
    background: rgba(255, 255, 255, .04);
    overflow: hidden;
    transition:
        background .2s ease,
        border-color .2s ease;
}

details:hover {
    background: rgba(255, 255, 255, .06);
    border-color: rgba(255, 255, 255, .2);
}

details summary {
    position: relative;
    padding: 18px 52px 18px 20px;
    color: var(--text);
    cursor: pointer;
    list-style: none;
}

details summary::-webkit-details-marker {
    display: none;
}

details summary::after {
    content: "▽";
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--sub);
    font-size: 1.2rem;
    transition: transform .2s ease;
}

details[open] summary::after {
    content: "△";
}

details p {
    margin: 0;
    padding: 0 20px 20px;
    color: var(--sub);
    line-height: 1.8;
}

/* class */
.box {
    position: relative;
    margin-bottom: 10px;
    padding: 32px 24px;

    background: #0f1626;

    border: 1px solid #c5a880;
    border-radius: 4px;
    box-shadow:
        0 10px 30px rgba(0, 0, 0, 0.5),
        inset 0 0 20px rgba(197, 168, 128, 0.05);
}

.box h3 {
    margin: 0 0 12px 0;
    font-size: 1.25rem;
    font-weight: 600;
    color: #d4af37;
    text-align: center;
    letter-spacing: 0.15em;
    text-shadow: 0 0 8px rgba(212, 175, 55, 0.2);
}

.box p {
    margin: 0;
    color: #e2e8f0;
    line-height: 1.8;
    text-align: justify;
}

.top-nav {
    position: fixed;
    top: 50%;
    left: 32px;
    transform: translateY(-50%);
    display: flex;
    flex-direction: column;
    gap: 24px;
    z-index: 10;
}

.menu-button {
    display: none;
}

/* 背景の星 */
.stars {
    position: fixed;
    inset: 0;
    pointer-events: none;

    background-image:
        radial-gradient(2px 2px at 5% 15%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 12% 72%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(2px 2px at 18% 45%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 27% 10%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(2px 2px at 36% 65%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 48% 28%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(2px 2px at 58% 82%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 65% 15%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(2px 2px at 72% 40%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 80% 70%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(2px 2px at 92% 18%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(1px 1px at 96% 52%, rgba(255, 255, 255, .8), transparent);

    animation: _twinkle 5s ease-in-out infinite;
}

/* 明滅用レイヤー */
.stars::before {
    content: "";
    position: absolute;
    inset: 0;

    background-image:
        radial-gradient(3px 3px at 20% 30%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(2px 2px at 60% 20%, rgba(255, 255, 255, .8), transparent),
        radial-gradient(3px 3px at 75% 60%, rgba(255, 255, 255, .9), transparent),
        radial-gradient(2px 2px at 35% 80%, rgba(255, 255, 255, .8), transparent);

    animation: _sparkle 3s ease-in-out infinite alternate;
}

@keyframes _twinkle {
    0% {
        opacity: .7;
    }

    50% {
        opacity: 1;
    }

    100% {
        opacity: .8;
    }
}

@keyframes _sparkle {
    0% {
        opacity: .2;
    }

    50% {
        opacity: 1;
    }

    100% {
        opacity: .3;
    }
}

/* スマホ用 */
@media(max-width:1000px) {

    main {
        font-size: 0.85rem;
        padding: 90px 24px;
    }

    .box h3 {
        font-size: 1.1rem;
    }

    .top-nav {
        top: auto;
        left: auto;
        right: 24px;
        bottom: 88px;
        transform: none;
        flex-direction: column;
        gap: 16px;
        padding: 18px 20px;
        border: 1px solid var(--line);
        border-radius: 18px;
        background: rgba(12, 21, 41, .9);
        backdrop-filter: blur(8px);
        opacity: 0;
        pointer-events: none;
        translate: 0 12px;
        transition: .25s;
    }

    .top-nav.is-open {
        opacity: 1;
        pointer-events: auto;
        translate: 0 0;
    }

    .menu-button {
        position: fixed;
        right: 24px;
        bottom: 24px;
        z-index: 11;

        display: flex;
        align-items: center;
        justify-content: center;

        width: 52px;
        height: 52px;

        padding: 0;

        color: var(--text);
        font-size: 1.1rem;
        line-height: 1;

        border: 1px solid var(--line);
        border-radius: 50%;

        background: rgba(255, 255, 255, .10);
        backdrop-filter: blur(8px);

        cursor: pointer;
    }
}