/* ============================================
   HighPurityEng - Professional Engineering Site
   Design Philosophy: Sophisticated, Clean, Technical
   ============================================ */

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

:root {
    /* Color Palette - Professional Engineering Aesthetic */
    --primary-dark: #1a2332;
    --primary-blue: #2c5aa0;
    --accent-blue: #3d7ec8;
    --light-gray: #f5f7fa;
    --medium-gray: #e0e6ed;
    --dark-gray: #4a5568;
    --text-dark: #1a202c;
    --text-light: #718096;
    --border-color: #cbd5e0;
    --white: #ffffff;
    
    /* Typography */
    --font-serif: 'Merriweather', serif;
    --font-sans: 'Lato', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Transitions */
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    color: var(--text-dark);
    background-color: var(--white);
    line-height: 1.6;
    font-size: 16px;
}

/* ============================================
   NAVIGATION
   ============================================ */

.navbar {
    background-color: var(--primary-dark);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

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

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--white);
    font-family: var(--font-serif);
    letter-spacing: 0.5px;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.nav-link {
    color: #b0b8c1;
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--accent-blue);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    right: 0;
    height: 2px;
    background-color: var(--accent-blue);
}

/* ============================================
   HERO SECTION
   ============================================ */

.hero {
    background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary-blue) 100%);
    color: var(--white);
    padding: var(--spacing-2xl) var(--spacing-lg);
    text-align: center;
    min-height: 400px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(61, 126, 200, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(61, 126, 200, 0.1) 0%, transparent 50%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 900px;
}

.hero-title {
    font-family: var(--font-serif);
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
    letter-spacing: -0.5px;
}

.hero-subtitle {
    font-size: 1.3rem;
    font-weight: 300;
    opacity: 0.95;
    line-height: 1.6;
}

/* ============================================
   CONTAINER & LAYOUT
   ============================================ */

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-lg);
}

/* ============================================
   ARTICLE STYLING
   ============================================ */

.article {
    background-color: var(--white);
}

.article-header {
    margin-bottom: var(--spacing-2xl);
    padding-bottom: var(--spacing-lg);
    border-bottom: 2px solid var(--medium-gray);
}

.article-title {
    font-family: var(--font-serif);
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin-bottom: var(--spacing-md);
    line-height: 1.3;
}

.article-meta {
    color: var(--text-light);
    font-size: 0.95rem;
    font-style: italic;
}

.article-content {
    font-size: 1.05rem;
    line-height: 1.8;
    color: var(--text-dark);
}

.article-content h2 {
    font-family: var(--font-serif);
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin-top: var(--spacing-2xl);
    margin-bottom: var(--spacing-md);
    padding-top: var(--spacing-lg);
}

.article-content p {
    margin-bottom: var(--spacing-lg);
    text-align: justify;
}

.article-content p:first-of-type::first-letter {
    font-size: 1.2em;
    font-weight: 700;
    color: var(--primary-blue);
}

.article-link {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 600;
    border-bottom: 2px solid transparent;
    transition: var(--transition);
}

.article-link:hover {
    border-bottom-color: var(--primary-blue);
    color: var(--accent-blue);
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
    background-color: var(--primary-dark);
    color: #b0b8c1;
    padding: var(--spacing-2xl) var(--spacing-lg);
    margin-top: var(--spacing-2xl);
    border-top: 2px solid var(--primary-blue);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
}

.footer-content p {
    margin-bottom: var(--spacing-sm);
    font-size: 0.95rem;
}

.footer-content p:first-child {
    font-weight: 600;
    color: var(--white);
}

/* ============================================
   FORMS
   ============================================ */

.form-group {
    margin-bottom: var(--spacing-lg);
}

label {
    display: block;
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
    color: var(--text-dark);
}

input[type="text"],
input[type="email"],
input[type="tel"],
textarea,
select {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    font-family: var(--font-sans);
    font-size: 1rem;
    color: var(--text-dark);
    background-color: var(--white);
    transition: var(--transition);
}

input[type="text"]:focus,
input[type="email"]:focus,
input[type="tel"]:focus,
textarea:focus,
select:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px rgba(44, 90, 160, 0.1);
}

textarea {
    resize: vertical;
    min-height: 150px;
}

button {
    background-color: var(--primary-blue);
    color: var(--white);
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: 4px;
    font-family: var(--font-sans);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

button:hover {
    background-color: var(--accent-blue);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(44, 90, 160, 0.3);
}

button:active {
    transform: translateY(0);
}

/* ============================================
   UTILITY CLASSES
   ============================================ */

.text-center {
    text-align: center;
}

.text-left {
    text-align: left;
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.mb-lg {
    margin-bottom: var(--spacing-lg);
}

.p-lg {
    padding: var(--spacing-lg);
}

.success-message {
    background-color: #c6f6d5;
    color: #22543d;
    padding: var(--spacing-md);
    border-radius: 4px;
    margin-bottom: var(--spacing-lg);
    border-left: 4px solid #48bb78;
}

.error-message {
    background-color: #fed7d7;
    color: #742a2a;
    padding: var(--spacing-md);
    border-radius: 4px;
    margin-bottom: var(--spacing-lg);
    border-left: 4px solid #f56565;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

@media (max-width: 768px) {
    .nav-menu {
        gap: var(--spacing-md);
    }

    .nav-link {
        font-size: 0.9rem;
    }

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

    .hero-subtitle {
        font-size: 1.1rem;
    }

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

    .article-content h2 {
        font-size: 1.5rem;
    }

    .container {
        padding: var(--spacing-lg) var(--spacing-md);
    }

    .article-content {
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .nav-container {
        flex-direction: column;
        gap: var(--spacing-md);
    }

    .nav-menu {
        flex-direction: column;
        gap: var(--spacing-sm);
        text-align: center;
    }

    .nav-link.active::after {
        display: none;
    }

    .hero {
        padding: var(--spacing-xl) var(--spacing-md);
        min-height: 300px;
    }

    .hero-title {
        font-size: 1.5rem;
    }

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

    .article-title {
        font-size: 1.5rem;
    }

    .article-content h2 {
        font-size: 1.3rem;
    }

    .container {
        padding: var(--spacing-lg) var(--spacing-sm);
    }

    .article-content {
        font-size: 0.95rem;
        line-height: 1.7;
    }

    .article-content p {
        text-align: left;
    }
}

/* ============================================
   PRINT STYLES
   ============================================ */

@media print {
    .navbar,
    .footer {
        display: none;
    }

    body {
        background-color: var(--white);
    }

    .article-content {
        color: #000;
    }
}