:root {
    --bg-color: #fdfbf7;
    --text-color: #5c4b43;
    --heading-color: #5c4b43;
    --container-bg: #fffef0;
    --border-color: #f0e6d2;
    --accent-color: #d98c5f;
}

:root.dark {
    --bg-color: #1a1614;
    --text-color: #fdfaf3;
    --heading-color: #fdfaf3;
    --container-bg: #2d241f;
    --border-color: #4a3a31;
    --accent-color: #f08547;
}

@media (prefers-color-scheme: dark) {
    :root:not(.light) {
        --bg-color: #1a1614;
        --text-color: #fdfaf3;
        --heading-color: #fdfaf3;
        --container-bg: #2d241f;
        --border-color: #4a3a31;
        --accent-color: #f08547;
    }
}

body {
    font-family: 'M PLUS Rounded 1c', 'Helvetica Neue', Arial, 'Hiragino Kaku Gothic ProN', 'Hiragino Sans', Meiryo, sans-serif;
    line-height: 1.8;
    color: var(--text-color);
    background-color: var(--bg-color);
    margin: 0;
    padding: 20px;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background-color: var(--container-bg);
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--border-color);
    transition: background-color 0.3s, border-color 0.3s;
}

.header-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

h1 {
    text-align: center;
    color: var(--heading-color);
    font-size: 2em;
    margin-bottom: 30px;
    border-bottom: 2px solid var(--accent-color);
    padding-bottom: 10px;
}

h2 {
    color: var(--heading-color);
    font-size: 1.4em;
    margin-top: 30px;
    margin-bottom: 15px;
    border-left: 4px solid var(--accent-color);
    padding-left: 10px;
}

p {
    margin-bottom: 15px;
    text-align: justify;
    text-justify: inter-ideograph;
}

ol {
    margin-bottom: 20px;
    padding-left: 25px;
}

li {
    margin-bottom: 10px;
}

.date-info {
    text-align: right;
    color: #7f8c8d;
    font-size: 0.9em;
    margin-top: 40px;
    border-top: 1px solid var(--border-color);
    padding-top: 20px;
}

.back-button {
    display: inline-flex;
    padding: 8px 16px;
    background-color: var(--container-bg);
    color: var(--accent-color);
    text-decoration: none;
    border-radius: 8px;
    border: 2px solid var(--border-color);
    font-weight: bold;
    transition: all 0.2s;
    box-shadow: 0 2px 0px var(--border-color);
}

.back-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 0px var(--border-color);
    border-color: var(--accent-color);
}

.theme-toggle {
    background-color: var(--container-bg);
    border: 2px solid var(--border-color);
    color: var(--text-color);
    border-radius: 50%;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: 0 2px 0px var(--border-color);
    transition: all 0.2s;
}

.theme-toggle:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 0px var(--border-color);
    color: var(--accent-color);
    border-color: var(--accent-color);
}

/* Icon visibility logic */
.theme-toggle .light-icon {
    display: none;
}

.theme-toggle .dark-icon {
    display: block;
}

:root.dark .theme-toggle .light-icon {
    display: block;
}

:root.dark .theme-toggle .dark-icon {
    display: none;
}

@media (prefers-color-scheme: dark) {
    :root:not(.light) .theme-toggle .light-icon {
        display: block;
    }

    :root:not(.light) .theme-toggle .dark-icon {
        display: none;
    }
}

.github-link {
    margin-top: 50px;
    padding-top: 20px;
    border-top: 1px dashed var(--border-color);
    display: flex;
    justify-content: flex-end;
}

.github-link a {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.9em;
    font-weight: bold;
    opacity: 0.7;
    transition: all 0.2s;
}

.github-link a:hover {
    opacity: 1;
    color: var(--accent-color);
}

.github-link .github-icon {
    width: 20px;
    height: 20px;
    fill: currentColor;
}