:root {
    --color-accent: #a3c4f3;

    --color-text-normal: #3f3f3f;

    --color-link-normal: #6a93c8;
    --color-link-hover: #93bde8;
    --color-link-active: #3d5f96;
    --color-link-visited: #7a8ab0;

    --bg-base: linear-gradient(135deg, #f5f5f5 0%, #eef2f3 50%, #e0eafc 100%);

    --glass-bg-surface: rgba(255, 255, 255, 0.4);
    --glass-bg: rgba(255, 255, 255, 0.8);
    --glass-border-surface: rgba(255, 255, 255, 0.6) 1px solid;
    --glass-border: rgba(255, 255, 255, 0.9) 1px solid;

    --shadow-box: 0 6px 32px rgba(0, 0, 0, 0.08);

    --container-width: 70vw;

    --heading-line: linear-gradient(to right, var(--color-accent), transparent);
}

html {
    background: var(--bg-base);
    background-attachment: fixed;
    min-height: 100vh;
    overflow-y: scroll;
    scrollbar-width: thin;
    scrollbar-color: rgba(163, 196, 243, 0.65) rgba(238, 242, 243, 0.8);
}

::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: rgba(238, 242, 243, 0.8); /* bg-baseの中間色に合わせた */
}

::-webkit-scrollbar-thumb {
    background: rgba(163, 196, 243, 0.65);
    border-radius: 999px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(163, 196, 243, 0.85);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    background: transparent;
    color: var(--color-text-normal);
    font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Noto Sans JP", sans-serif;
    min-height: 100vh;
}

/* site-header */

#site-header {
    background: var(--glass-bg-surface);
    backdrop-filter: blur(12px);
    border-bottom: var(--glass-border-surface);
    box-shadow: var(--shadow-box);
    margin-bottom: 1.5rem;
    position: sticky;
    top: 0;
    width: 100%;
    z-index: 100;
}

.site-title {
    font-family: 'Zen Old Mincho', serif;
    font-size: 1.5rem;
    font-weight: 400;
    margin: 0 auto;
    padding-block: 1.25rem;
    padding-inline: 0.5rem;
    width: var(--container-width);
}

.site-title a {
    color: var(--color-text-normal);
    cursor: pointer;
    text-decoration: none;
}

/* home */

main.home {
    margin: 0 auto;
    width: var(--container-width);
    z-index: 0;
}

.home-links {
    display: grid;
    gap: 1rem;
    grid-template-columns: repeat(3, 1fr);
}

.home-category {
    background: var(--glass-bg);
    border: var(--glass-border);
    border-radius: 1rem;
    box-shadow: var(--shadow-box);
    padding-block: 1rem;
    padding-inline: 1.5rem;
}

.home-category h2 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    padding-bottom: 0.5rem;
    padding-inline: 0.5rem;
    position: relative;
}

.home-category h2::after {
    background: var(--heading-line);
    bottom: 0;
    content: "";
    height: 2px;
    left: 0;
    position: absolute;
    width: 100%;
}

.home-category h2 a {
    color: var(--color-text-normal);
    text-decoration: none;
    transition: color 0.2s ease;
}

.home-category h2 a:hover {
    color: var(--color-link-hover);
}

.home-category h2 a:active {
    color: var(--color-link-active);
}

.home-category nav {
    padding-inline: 0.5rem;
}

.home-category nav a {
    color: var(--color-text-normal);
    display: block;
    padding-block: 0.25rem;
    text-decoration: none;
    transition: color 0.2s ease;
}

.home-category nav a:hover {
    color: var(--color-link-hover);
}

.home-category nav a:active {
    color: var(--color-link-active);
}

.home-category nav button {
    background: none;
    border: none;
    color: var(--color-text-normal);
    cursor: pointer;
    font-size: 1rem;
    font-weight: bold;
    padding-block: 0.25rem;
    transition: color 0.2s ease;
}

.home-category nav button:hover {
    color: var(--color-link-hover);
}

.home-category nav button:active {
    color: var(--color-link-active);
}

.home-category .extra-wrapper {
    display: grid;
    grid-template-rows: 0fr;
    overflow: hidden;
    transition: grid-template-rows 0.4s ease;
}

.home-category .extra-wrapper.is-open {
    grid-template-rows: 1fr;
}

.home-category .extra-content {
    min-height: 0px;
    display: flex;
    flex-direction: column;
}

.home-about {
    background: var(--glass-bg);
    border: var(--glass-border);
    border-radius: 1rem;
    box-shadow: var(--shadow-box);
    margin-top: 1.5rem;
    padding-block: 1.25rem;
    padding-inline: 1.5rem;
}

.home-about h2 {
    margin-bottom: 0.75rem;
    padding-bottom: 0.5rem;
    padding-inline: 0.5rem;
    position: relative;
}

.home-about h2::after {
    background: var(--heading-line);
    bottom: 0;
    content: "";
    height: 2px;
    left: 0;
    position: absolute;
    width: 100%;
}

.home-about p {
    line-height: 2;
    margin-block: 0.25rem;
    padding-inline: 0.5rem;
}

.home-about a {
    color: var(--color-link-normal);
    text-decoration: none;
    transition: color 0.2s ease;
}

.home-about a:hover {
    color: var(--color-link-hover);
}

.home-about a:active {
    color: var(--color-link-active);
}

/* main-page */

main.page {
    margin: 0 auto;
    width: var(--container-width);
}

main.page .container {
    display: grid;
    gap: 1.25rem;
    grid-template-columns: 7fr 3fr;
}

.main-content {
    background: var(--glass-bg);
    border: var(--glass-border);
    border-radius: 1rem;
    box-shadow: var(--shadow-box);
    padding-block: 1.25rem;
    padding-inline: 1.5rem;
}

.main-content .title-wrapper {
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    margin-bottom: 0.75rem;
}

.main-content h1 {
    font-size: 1.65rem;
    padding-bottom: 0.75rem;
    margin-top: 0.25rem;
}

.main-content time.update-date {
    font-size: 15px;
    padding: 0;
    margin-left: 0.125rem;
}

.main-content h2 {
    margin-bottom: 0.25rem;
}

.main-content h3 {
    margin-top: 0.75rem;
}

.main-content p {
    line-height: 2;
    padding-block: 0.25rem;
}

.main-content section {
    margin-bottom: 1.5rem;
}

.main-content a {
    color: var(--color-link-normal);
    text-decoration: none;
    transition: color 0.2s ease;
}

.main-content a:hover {
    color: var(--color-link-hover);
}

.main-content a:active {
    color: var(--color-link-active);
}

.main-content a:visited {
    color: var(--color-link-visited);
}

.main-content a:visited:hover {
    color: var(--color-link-hover);
}

.main-content a:visited:active {
    color: var(--color-link-active);
}

.sidebar {
    background: var(--glass-bg);
    border: var(--glass-border);
    border-radius: 1rem;
    box-shadow: var(--shadow-box);
}

a .material-symbols-outlined {
    font-size: 1.1225em;
    vertical-align: text-bottom;
}

/* sidebar */

.sidebar {
    padding-block: 0.75rem;
    padding-inline: 1rem;
}

.sidebar img.profile {
    border-radius: 50%;
    width: 75%;
}

.sidebar section {
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    padding-bottom: 0.75rem;
}

.sidebar h2 {
    font-size: 1.4rem;
    padding-block: 0.25rem;
    padding-left: 0.5rem;
    position: relative;
}

.sidebar h2::before {
    background: var(--color-accent);
    border-radius: 2px;
    content: "";
    height: 100%;
    left: 0;
    position: absolute;
    top: 0;
    width: 4px;
}

.sidebar p {
    font-size: 0.95rem;
    line-height: 2;
}

/* footer */

#site-footer {
    background: var(--glass-bg);
    border-top: var(--glass-border-surface);
    box-shadow: var(--shadow-box);
    margin-top: 1.5rem;
}

#site-footer p {
    font-size: 15px;
    padding-block: 1.25rem;
    text-align: center;
}

/* for tablet */

@media (max-width: 1199px) {
    :root {
        --container-width: 80vw;
    }

    .home-links {
        grid-template-columns: repeat(2, 1fr);
    }

    main.page .container {
        grid-template-columns: 1fr;
    }
}

/* for phone */

@media (max-width: 768px) {
    :root {
        --container-width: 95vw;
    }

    .home-links {
        grid-template-columns: 1fr;
    }

    main.page .container {
        grid-template-columns: 1fr;
    }
}