:root {
    --bg-main: #00293c;
    --bg-gradient-start: #0a3a50;
    --bg-card: #00293c;
    --text-primary: #d0e1f9;
    --text-secondary: #d0e1f9;
    --accent-red: #d70026;
    --accent-teal: #1e656d;
    --glow-color: rgba(29, 101, 109, 0.8);
}

body {
    font-family: 'Noto Sans JP', sans-serif;
    line-height: 1.8;
    background-color: var(--bg-main);
    background-image: radial-gradient(circle at top left, var(--bg-gradient-start), var(--bg-main) 50%);
    color: var(--text-primary);
    margin: 0;
    padding: 25px 15px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
}

header {
    margin-bottom: 50px;
    border-left: 5px solid var(--accent-red);
    padding: 10px 0 10px 25px;
}

header h1 {
    font-size: 2.2em;
    font-weight: 800;
    letter-spacing: 1px;
    color: var(--text-primary);
    margin: 0 0 10px 0;
    text-shadow: 0 0 10px rgba(215, 0, 38, 0.3);
}

header p {
    color: var(--text-secondary);
    max-width: 600px;
    font-size: 1.1em;
}

.table-of-contents {
    background-color: transparent;
    border: none;
    margin-bottom: 50px;
}

.table-of-contents h2 {
    font-size: 1.2em;
    text-align: left;
    margin-bottom: 20px;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--text-secondary);
}

.table-of-contents ul {
    list-style: none;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    justify-content: flex-start;
    gap: 15px;
}

.table-of-contents ul a {
    display: block;
    background-color: var(--accent-teal);
    color: var(--text-primary);
    padding: 8px 18px;
    border-radius: 20px;
    font-weight: bold;
    text-decoration: none;
    transition: background-color 0.3s ease, transform 0.3s ease;
    box-shadow: 0 4px 15px -5px var(--glow-color);
}

.table-of-contents ul a:active {
    background-color: var(--accent-red);
    transform: scale(0.95);
}

.card {
    background-color: var(--bg-card);
    padding: 30px;
    margin-bottom: 30px;
    border-radius: 12px;
    border: 1px solid var(--accent-teal);
    box-shadow: 0 10px 30px -15px var(--glow-color),
                inset 0 0 15px rgba(29, 101, 109, 0.3);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

h2 {
    font-size: 1.8em;
    font-weight: 700;
    color: var(--text-primary);
    margin-top: 0;
    margin-bottom: 25px;
    padding-bottom: 15px;
    border-bottom: 2px solid;
    border-image: linear-gradient(to right, var(--accent-teal), transparent) 1;
}

h3 {
    font-size: 1.4em;
    color: var(--text-primary);
    margin-top: 40px;
    position: relative;
    padding-left: 20px;
}

h3::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 8px;
    height: 8px;
    background-color: var(--accent-red);
    border-radius: 50%;
    box-shadow: 0 0 10px var(--accent-red);
}

h4 {
    font-size: 1.1em;
    color: var(--text-secondary);
    margin-top: 25px;
}

ul, ol, dl {
    padding-left: 0;
}

ul li {
    margin-bottom: 15px;
    color: var(--text-secondary);
    list-style: none;
    position: relative;
    padding-left: 25px;
}

ul li::before {
    content: '›';
    position: absolute;
    left: 0;
    color: var(--accent-teal);
    font-weight: bold;
    font-size: 1.5em;
    line-height: 1;
}

ul li strong {
    color: var(--text-primary);
}

a {
    color: var(--accent-red);
    text-decoration: none;
    font-weight: bold;
    background-image: linear-gradient(to right, var(--accent-red), var(--accent-red));
    background-position: bottom left;
    background-repeat: no-repeat;
    background-size: 0% 2px;
    transition: background-size 0.3s ease;
}

a:hover, a:focus {
    background-size: 100% 2px;
}

dl dt {
    font-weight: bold;
    color: var(--text-primary);
    margin-top: 20px;
    background: rgba(29, 101, 109, 0.2);
    padding: 5px 10px;
    border-radius: 4px;
}

dl dd {
    margin-left: 0;
    padding: 10px 0 10px 15px;
    border-left: 3px solid var(--accent-teal);
    color: var(--text-secondary);
}

footer {
    text-align: center;
    margin-top: 50px;
    padding-top: 20px;
    border-top: 1px solid var(--accent-teal);
    color: var(--text-secondary);
    font-size: 0.9em;
}

@media (max-width: 600px) {
    header h1 {
        font-size: 1.8em;
    }
    .card {
        padding: 20px;
    }
}