:root {
    --bg-dark: #0a0a0f;
    --bg-card: #12121a;
    --bg-card-hover: #181825;
    --klein-blue: #002FA7;
    --klein-blue-light: #1a45c9;
    --light-blue: #74c0fc;
    --light-blue-soft: #a5d8ff;
    --text-white: #ffffff;
    --text-light: #e9ecef;
    --text-muted: #adb5bd;
    --border-color: rgba(0, 47, 167, 0.3);
    --border-color-hover: rgba(0, 47, 167, 0.6);
    --success: #51cf66;
}

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

body {
    font-family: 'Noto Serif SC', serif;
    background: var(--bg-dark);
    color: var(--text-white);
    line-height: 1.7;
    overflow-x: hidden;
}

.bg-pattern {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(circle at 15% 85%, rgba(0, 47, 167, 0.08) 0%, transparent 50%),
        radial-gradient(circle at 85% 15%, rgba(116, 192, 252, 0.06) 0%, transparent 50%);
    pointer-events: none;
    z-index: 0;
}

nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 1rem 2rem;
    background: rgba(10, 10, 15, 0.95);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--light-blue);
    text-decoration: none;
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    list-style: none;
}

.nav-links a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.95rem;
    padding: 0.3rem 0;
    transition: color 0.3s;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--light-blue);
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section {
    position: relative;
    padding: 4rem 0;
    z-index: 1;
}

.section-title {
    font-size: 2rem;
    margin-bottom: 2rem;
    color: var(--light-blue);
    border-bottom: 2px solid var(--klein-blue);
    padding-bottom: 0.5rem;
}

.module-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.module-card h3 {
    color: var(--light-blue);
    font-size: 1.3rem;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.module-card h3::before {
    content: "◆";
    color: var(--klein-blue-light);
}

.module-card h4 {
    color: var(--text-light);
    font-size: 1.1rem;
    margin: 1.5rem 0 0.8rem;
}

.module-card p {
    color: var(--text-muted);
    margin-bottom: 1rem;
    font-size: 0.95rem;
}

.tip-box {
    background: rgba(81, 207, 102, 0.1);
    border-left: 3px solid var(--success);
    padding: 1rem;
    margin: 1rem 0;
    border-radius: 0 8px 8px 0;
}

.tip-box strong {
    color: var(--success);
    display: block;
    margin-bottom: 0.5rem;
}

.example-box {
    background: rgba(0, 47, 167, 0.15);
    border: 1px solid var(--border-color);
    padding: 1rem;
    margin: 1rem 0;
    border-radius: 8px;
}

.example-box strong {
    color: var(--light-blue);
    display: block;
    margin-bottom: 0.5rem;
}

.example-box code {
    background: var(--bg-dark);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-size: 0.9rem;
    color: var(--light-blue-soft);
    display: block;
    margin-top: 0.5rem;
}

.key-points {
    list-style: none;
    margin: 1rem 0;
}

.key-points li {
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
    color: var(--text-muted);
}

.key-points li::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: var(--success);
    font-weight: bold;
}

footer {
    position: relative;
    z-index: 1;
    text-align: center;
    padding: 2rem;
    border-top: 1px solid var(--border-color);
    margin-top: 2rem;
}

footer p {
    color: var(--text-light);
    font-size: 0.95rem;
}

footer p:last-child {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-top: 0.3rem;
}

.back-btn {
    display: inline-block;
    padding: 0.7rem 1.5rem;
    background: var(--klein-blue);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    margin-bottom: 2rem;
    transition: all 0.3s;
}

.back-btn:hover {
    background: var(--klein-blue-light);
    transform: translateY(-2px);
}

.method-steps {
    counter-reset: step;
}

.method-step {
    position: relative;
    padding-left: 3rem;
    margin-bottom: 1.5rem;
}

.method-step::before {
    counter-increment: step;
    content: counter(step);
    position: absolute;
    left: 0;
    top: 0;
    width: 2rem;
    height: 2rem;
    background: var(--klein-blue);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1rem;
}

.method-step h4 {
    color: var(--text-light);
    margin-bottom: 0.5rem;
}

.method-step p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    .section-title {
        font-size: 1.6rem;
    }
}