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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background: #f5f5f5;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

header {
    background: linear-gradient(135deg, #ff6b9d, #ff8c42);
    color: white;
    padding: 15px 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 24px;
    font-weight: bold;
}

nav a {
    color: white;
    text-decoration: none;
    margin-left: 30px;
    font-weight: 500;
    transition: opacity 0.3s;
}

nav a:hover {
    opacity: 0.8;
}

.hero {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    padding: 80px 0;
    text-align: center;
}

.hero h1 {
    font-size: 48px;
    margin-bottom: 20px;
}

.hero p {
    font-size: 20px;
    opacity: 0.9;
}

.hero .cta-btn {
    display: inline-block;
    margin-top: 30px;
    padding: 15px 40px;
    background: white;
    color: #764ba2;
    text-decoration: none;
    border-radius: 30px;
    font-weight: bold;
    font-size: 18px;
    transition: transform 0.3s, box-shadow 0.3s;
}

.hero .cta-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

/* Section titles */
.section-title {
    font-size: 32px;
    margin: 60px 0 30px;
    color: #333;
    text-align: center;
}

/* Card grid layout */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
    margin-bottom: 40px;
}

/* Card styles */
.card {
    display: block;
    background: white;
    border-radius: 16px;
    padding: 35px 30px;
    text-decoration: none;
    color: inherit;
    box-shadow: 0 4px 15px rgba(0,0,0,0.08);
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 30px rgba(0,0,0,0.15);
    border-color: #ff6b9d;
}

.card-icon {
    font-size: 48px;
    margin-bottom: 15px;
    display: block;
}

.card h3 {
    font-size: 22px;
    margin-bottom: 12px;
    color: #333;
    font-weight: 600;
}

.card p {
    color: #666;
    line-height: 1.7;
    font-size: 15px;
}

/* Tips section */
.tips-section {
    background: white;
    padding: 60px 0;
    margin-top: 40px;
}

.tips-section .section-title {
    margin-top: 0;
}

.tip-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 25px;
}

.tip-card {
    background: #fafafa;
    border-radius: 12px;
    padding: 25px;
    border-left: 4px solid #ff6b9d;
}

.tip-card h3 {
    font-size: 18px;
    color: #ff6b9d;
    margin-bottom: 10px;
}

.tip-card p {
    color: #666;
    font-size: 14px;
    line-height: 1.7;
}

/* Article pages */
.article {
    max-width: 900px;
    margin: 40px auto;
    padding: 0 20px;
}

.article h1 {
    font-size: 32px;
    margin-bottom: 10px;
    color: #333;
}

.article .meta {
    color: #888;
    font-size: 14px;
    margin-bottom: 30px;
}

.article h2 {
    font-size: 24px;
    margin: 40px 0 15px;
    color: #ff6b9d;
    border-left: 4px solid #ff6b9d;
    padding-left: 12px;
}

.article h3 {
    font-size: 18px;
    margin: 25px 0 10px;
    color: #444;
}

.article p {
    line-height: 1.9;
    color: #444;
    margin-bottom: 15px;
}

.article ul {
    padding-left: 20px;
    line-height: 2;
    color: #444;
}

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

.tip-box {
    background: #fff5f8;
    border-left: 4px solid #ff6b9d;
    padding: 15px 20px;
    margin: 20px 0;
    border-radius: 0 8px 8px 0;
}

.danger-box {
    background: #fff0f0;
    border-left: 4px solid #f44336;
    padding: 15px 20px;
    margin: 20px 0;
    border-radius: 0 8px 8px 0;
}

.pro-box {
    background: #f0f8ff;
    border-left: 4px solid #2196f3;
    padding: 15px 20px;
    margin: 20px 0;
    border-radius: 0 8px 8px 0;
}

.skill-tag {
    display: inline-block;
    padding: 2px 8px;
    background: #ff6b9d;
    color: #fff;
    border-radius: 4px;
    font-size: 12px;
    margin-right: 5px;
}

.skill-tag.easy {
    background: #4caf50;
}

.skill-tag.medium {
    background: #ff9800;
}

.skill-tag.hard {
    background: #f44336;
}

.skill-tag.black {
    background: #333;
}

/* Footer */
footer {
    background: #333;
    color: white;
    padding: 40px 0;
    text-align: center;
    margin-top: 60px;
}

footer p {
    margin: 10px 0;
    opacity: 0.8;
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 32px;
    }
    
    header .container {
        flex-direction: column;
        gap: 15px;
    }
    
    nav a {
        margin: 0 15px;
    }
    
    .card-grid {
        grid-template-columns: 1fr;
    }
    
    .tip-grid {
        grid-template-columns: 1fr;
    }
}