/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8fafc;
}

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

/* Header and Navigation */
.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.logo h1 {
    color: white;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 0.2rem;
}

.tagline {
    color: rgba(255,255,255,0.8);
    font-size: 0.9rem;
    font-weight: 300;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    position: relative;
}

.nav-link:hover {
    color: #ffd700;
    transform: translateY(-2px);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: #ffd700;
    transition: width 0.3s ease;
}

.nav-link:hover::after {
    width: 100%;
}

/* Hamburger menu */
.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: white;
    margin: 3px 0;
    transition: 0.3s;
}

.hamburger.active span:nth-child(1) {
    transform: rotate(-45deg) translate(-5px, 6px);
}

.hamburger.active span:nth-child(2) {
    opacity: 0;
}

.hamburger.active span:nth-child(3) {
    transform: rotate(45deg) translate(-5px, -6px);
}

/* Main content */
.main {
    margin-top: 80px;
}

/* Hero section */
.hero-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.hero-subtitle {
    font-size: 1.2rem;
    margin-bottom: 3rem;
    opacity: 0.9;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 3rem;
}

.feature {
    background: rgba(255,255,255,0.1);
    padding: 2rem;
    border-radius: 15px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255,255,255,0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    display: block;
}

.feature h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

.feature p {
    opacity: 0.9;
    font-size: 0.95rem;
}

/* Calculator section */
.calculator-section {
    padding: 4rem 0;
    background: white;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: #2d3748;
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 2px;
}

.calculator-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: start;
}

.calculator-form {
    background: #f7fafc;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    border: 1px solid #e2e8f0;
}

.input-group {
    margin-bottom: 1.5rem;
    position: relative;
}

.input-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: #2d3748;
}

.input-group input {
    width: 100%;
    padding: 0.75rem 3rem 0.75rem 1rem;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
    background: white;
}

.input-group input:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.unit {
    position: absolute;
    right: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: #718096;
    font-weight: 600;
    margin-top: 1.25rem;
}

.calculate-btn {
    width: 100%;
    padding: 1rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-bottom: 1.5rem;
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.result {
    background: white;
    padding: 1.5rem;
    border-radius: 8px;
    border: 2px solid #e2e8f0;
    text-align: center;
}

.result-label {
    display: block;
    font-weight: 600;
    color: #2d3748;
    margin-bottom: 0.5rem;
}

.result-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: #667eea;
}

.formula-explanation {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    border: 1px solid #e2e8f0;
}

.formula-explanation h3 {
    color: #2d3748;
    margin-bottom: 1rem;
    font-size: 1.3rem;
    padding: 1rem;
    background: #f7fafc;
    border-radius: 8px;
    border-left: 4px solid #667eea;
}

.formula-explanation p {
    color: #4a5568;
    line-height: 1.7;
}

/* Blog section */
.blog-section {
    padding: 4rem 0;
    background: #f7fafc;
}

.blog-article {
    background: white;
    border-radius: 15px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    overflow: hidden;
    border: 1px solid #e2e8f0;
}

.article-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 3rem 2rem 2rem;
    text-align: center;
}

.article-title {
    font-size: 2.2rem;
    font-weight: 700;
    margin-bottom: 1rem;
    line-height: 1.3;
}

.article-meta {
    display: flex;
    justify-content: center;
    gap: 2rem;
    opacity: 0.9;
    font-size: 0.95rem;
}

.article-content {
    padding: 3rem;
    max-width: none;
}

.article-intro {
    font-size: 1.1rem;
    color: #4a5568;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background: #f7fafc;
    border-radius: 8px;
    border-left: 4px solid #667eea;
    line-height: 1.7;
}

.article-content h3 {
    color: #2d3748;
    font-size: 1.5rem;
    margin: 2.5rem 0 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid #e2e8f0;
}

.article-content h4 {
    color: #4a5568;
    font-size: 1.2rem;
    margin: 2rem 0 1rem;
}

.article-content p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
    color: #4a5568;
}

.article-content ul, .article-content ol {
    margin: 1.5rem 0;
    padding-left: 2rem;
}

.article-content li {
    margin-bottom: 0.5rem;
    line-height: 1.6;
    color: #4a5568;
}

.article-content a {
    color: #667eea;
    text-decoration: none;
    font-weight: 600;
    border-bottom: 2px solid transparent;
    transition: all 0.3s ease;
}

.article-content a:hover {
    color: #764ba2;
    border-bottom-color: #764ba2;
}

.article-content strong {
    color: #2d3748;
    font-weight: 600;
}

/* Footer */
.footer {
    background: #2d3748;
    color: white;
    padding: 3rem 0 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3, .footer-section h4 {
    margin-bottom: 1rem;
    color: #ffd700;
}

.footer-section p {
    opacity: 0.8;
    line-height: 1.6;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section ul li a {
    color: rgba(255,255,255,0.8);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-section ul li a:hover {
    color: #ffd700;
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid #4a5568;
    opacity: 0.8;
}

/* Responsive design */
@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        left: -100%;
        top: 80px;
        flex-direction: column;
        background: rgba(102, 126, 234, 0.95);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        backdrop-filter: blur(10px);
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-menu li {
        margin: 1rem 0;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .calculator-container {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .article-title {
        font-size: 1.8rem;
    }

    .article-content {
        padding: 2rem 1.5rem;
    }

    .article-meta {
        flex-direction: column;
        gap: 0.5rem;
    }

    .section-title {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .hero-section {
        padding: 2rem 0;
    }

    .hero-title {
        font-size: 1.8rem;
    }

    .calculator-section, .blog-section {
        padding: 2rem 0;
    }

    .article-content {
        padding: 1.5rem 1rem;
    }

    .article-content h3 {
        font-size: 1.3rem;
    }

    .feature {
        padding: 1.5rem;
    }
}

/* Animations and transitions */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.feature, .calculator-form, .formula-explanation, .blog-article {
    animation: fadeInUp 0.6s ease-out;
}

/* Smooth scrolling enhancement */
@media (prefers-reduced-motion: no-preference) {
    html {
        scroll-behavior: smooth;
    }
}

/* Focus styles for accessibility */
button:focus, input:focus, a:focus {
    outline: 2px solid #667eea;
    outline-offset: 2px;
}

/* Print styles */
@media print {
    .header, .footer, .calculator-section {
        display: none;
    }
    
    .blog-article {
        box-shadow: none;
        border: 1px solid #ccc;
    }
    
    .article-content a {
        color: #000;
        text-decoration: underline;
    }
}