* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: "Hiragino Kaku Gothic ProN",
        "Yu Gothic",
        "Meiryo",
        sans-serif;
    background: linear-gradient(
        180deg,
        #fff8f0 0%,
        #fff3ea 50%,
        #f8eee7 100%
    );
    color: #3a302b;
}

header {
    position: relative;
    overflow: hidden;
    text-align: center;
    padding: 90px 20px 70px;
    background: linear-gradient(
        180deg,
        #8bd3f7 0%,
        #ccefff 70%,
        #f4fbff 100%
    );
    color: #4a332f;
}

header::before {
    content: "";
    position: absolute;
    inset: 0;
    background: linear-gradient(
        180deg,
        #776fae 0%,
        #b982bd 25%,
        #e89ca6 55%,
        #f4ad7d 78%,
        #ffd09c 100%
    );
    opacity: 0;
    animation: sunsetFade 4s ease-in-out forwards;
}

header::after {
    content: "";
    position: absolute;
    width: 190px;
    height: 190px;
    top: 20px;
    right: 10%;
    border-radius: 50%;
    background: radial-gradient(
        circle,
        rgba(255, 247, 213, 0.9) 0%,
        rgba(255, 228, 170, 0.45) 45%,
        rgba(255, 220, 160, 0) 75%
    );
    filter: blur(4px);
    animation: sunMove 4s ease-in-out forwards;
}

header h1,
header p,
header nav {
    position: relative;
    z-index: 1;
}

header h1 {
    margin: 0;
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 700;
    letter-spacing: 0.12em;
    text-shadow: 0 2px 10px rgba(255, 255, 255, 0.25);
}

header p {
    margin-top: 14px;
    font-size: 1rem;
    letter-spacing: 0.04em;
    color: #5c4540;
}

nav {
    margin-top: 28px;
}

nav a {
    display: inline-block;
    margin: 5px 6px;
    padding: 9px 16px;
    color: #4d3833;
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 600;
    background: rgba(255, 255, 255, 0.28);
    border: 1px solid rgba(255, 255, 255, 0.4);
    border-radius: 999px;
    backdrop-filter: blur(4px);
    transition: transform 0.2s ease,
        background-color 0.2s ease,
        box-shadow 0.2s ease;
}

nav a:hover {
    transform: translateY(-2px);
    background: rgba(255, 255, 255, 0.45);
    box-shadow: 0 6px 15px rgba(85, 55, 45, 0.12);
}

main {
    max-width: 950px;
    margin: 55px auto;
    padding: 0 20px;
}

section {
    margin-bottom: 32px;
    padding: 36px;
    background: rgba(255, 255, 255, 0.78);
    border: 1px solid rgba(110, 75, 60, 0.08);
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(90, 55, 40, 0.07);
    backdrop-filter: blur(5px);
    transition: transform 0.2s ease,
        box-shadow 0.2s ease;
}

section:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 35px rgba(90, 55, 40, 0.1);
}

h2 {
    margin-top: 0;
    margin-bottom: 20px;
    font-size: 1.55rem;
    color: #513a30;
}

h2::after {
    content: "";
    display: block;
    width: 48px;
    height: 3px;
    margin-top: 10px;
    background: linear-gradient(
        90deg,
        #e99b6a,
        #eab3a9,
        #b997c7
    );
    border-radius: 999px;
}

h3 {
    color: #60463b;
}

p {
    line-height: 1.9;
}

main a {
    color: #9b5d47;
}

#join a {
    display: inline-block;
    margin-top: 10px;
    padding: 12px 22px;
    text-decoration: none;
    color: white;
    background: linear-gradient(
        135deg,
        #e89b72,
        #d98181
    );
    border-radius: 999px;
    font-weight: bold;
    box-shadow: 0 6px 16px rgba(190, 105, 90, 0.22);
    transition: transform 0.2s ease,
        box-shadow 0.2s ease;
}

#join a:hover {
    transform: translateY(-2px);
    box-shadow: 0 9px 22px rgba(190, 105, 90, 0.3);
}

footer {
    text-align: center;
    padding: 32px 20px;
    background: linear-gradient(
        180deg,
        #4e3b45,
        #352d35
    );
    color: #d7cbd1;
    font-size: 0.9rem;
}

@keyframes sunsetFade {
    0% {
        opacity: 0;
    }

    20% {
        opacity: 0;
    }

    100% {
        opacity: 1;
    }
}

@keyframes sunMove {
    0% {
        transform: translateY(-15px)
            scale(1.05);
        opacity: 0.65;
    }

    100% {
        transform: translateY(55px)
            scale(0.9);
        opacity: 0.4;
    }
}

@media (max-width: 700px) {
    header {
        padding: 70px 16px 55px;
    }

    header h1 {
        letter-spacing: 0.07em;
    }

    header::after {
        width: 140px;
        height: 140px;
        right: 0;
    }

    main {
        margin: 35px auto;
        padding: 0 14px;
    }

    section {
        padding: 26px 22px;
        border-radius: 16px;
    }

    nav a {
        font-size: 0.88rem;
        padding: 8px 12px;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation: none !important;
        transition: none !important;
    }

    header::before {
        opacity: 1;
    }
}

ul {
    padding-left: 1.5rem;
    line-height: 2;
}

li {
    margin-bottom: 6px;
}

blockquote {
    margin: 24px 0;
    padding: 18px 22px;
    background: rgba(255, 220, 190, 0.35);
    border-left: 4px solid #e89b72;
    border-radius: 10px;
    line-height: 1.8;
}

code {
    padding: 2px 6px;
    background: rgba(90, 70, 60, 0.08);
    border-radius: 5px;
}

.toc ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.toc li {
    margin-bottom: 8px;
}

.toc a {
    display: block;
    padding: 10px 14px;
    text-decoration: none;
    color: #5a4035;
    background: rgba(255, 255, 255, 0.45);
    border: 1px solid rgba(110, 75, 60, 0.12);
    border-radius: 10px;
    transition: 0.2s;
}

.toc a:hover {
    transform: translateX(4px);
    background: rgba(255, 230, 210, 0.7);
    border-color: rgba(110, 75, 60, 0.2);
}

#join {
    text-align: center;
    padding: 60px 30px;
}

#join h2 {
    font-size: clamp(2rem, 5vw, 3rem);
    margin-bottom: 20px;
}

#join p {
    font-size: 1.15rem;
    margin-bottom: 28px;
}

#join a {
    display: inline-block;
    padding: 14px 28px;
    font-size: 1.05rem;
    font-weight: bold;
    text-decoration: none;
    color: white;
    background: linear-gradient(
        135deg,
        #e89b72,
        #d98181
    );
    border-radius: 999px;
    box-shadow: 0 8px 20px rgba(190, 105, 90, 0.25);
    transition: 0.2s;
}

#join a:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 28px rgba(190, 105, 90, 0.32);
}