/* ===================================
   ThermoFluidCalc - Main Stylesheet
   =================================== */

/* CSS Reset & Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #0066cc;
    --primary-dark: #004d99;
    --primary-light: #3385d6;
    --secondary-color: #ff6b35;
    --text-dark: #1a1a1a;
    --text-light: #666666;
    --background: #ffffff;
    --background-alt: #f8f9fa;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.15);
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--background);
    font-size: 16px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 2rem;
}

h3 {
    font-size: 1.5rem;
}

p {
    margin-bottom: 1rem;
    color: var(--text-light);
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--primary-dark);
}

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

/* Header & Navigation */
header {
    background-color: var(--background);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

header nav {
    padding: 1rem 0;
}

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

/* Logo Styles */
.logo-container {
    display: flex;
    align-items: center;
}

.logo-container a {
    display: block;
    line-height: 0;
}

.logo {
    height: 75px;
    width: auto;
    transition: var(--transition);
}

.logo:hover {
    opacity: 0.8;
    transform: scale(1.02);
}

header ul {
    list-style: none;
    display: flex;
    gap: 2rem;
    margin: 0;
}

header ul li a {
    color: var(--text-dark);
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: var(--transition);
}

header ul li a:hover {
    background-color: var(--background-alt);
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 5rem 0;
    text-align: center;
}

.hero h2 {
    color: white;
    font-size: 2.75rem;
    margin-bottom: 1.5rem;
    font-weight: 700;
}

.hero p {
    color: rgba(255, 255, 255, 0.9);
    font-size: 1.25rem;
    max-width: 700px;
    margin: 0 auto 2rem;
}

.cta-button {
    display: inline-block;
    background-color: var(--secondary-color);
    color: white;
    padding: 1rem 2.5rem;
    border-radius: 50px;
    font-weight: 600;
    font-size: 1.1rem;
    transition: var(--transition);
    box-shadow: var(--shadow-lg);
}

.cta-button:hover {
    background-color: #ff5722;
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(255, 107, 53, 0.4);
}

/* Features Section */
.features {
    padding: 5rem 0;
    background-color: var(--background-alt);
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--text-dark);
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.feature-card {
    background-color: var(--background);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

.feature-card h3 {
    color: var(--primary-color);
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.feature-card p {
    color: var(--text-light);
    line-height: 1.7;
}

/* About Section */
.about {
    padding: 5rem 0;
    background-color: var(--background);
}

.about h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: var(--text-dark);
}

.about p {
    max-width: 800px;
    margin: 0 auto;
    font-size: 1.1rem;
    line-height: 1.8;
    text-align: center;
    color: var(--text-light);
}

/* Footer */
footer {
    background-color: var(--text-dark);
    color: white;
    padding: 3rem 0 2rem;
    margin-top: 4rem;
}

footer .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1.5rem;
}

footer p {
    color: rgba(255, 255, 255, 0.8);
    margin: 0;
}

footer nav {
    display: flex;
    gap: 2rem;
}

footer nav a {
    color: rgba(255, 255, 255, 0.8);
    transition: var(--transition);
}

footer nav a:hover {
    color: white;
}

/* Responsive Design */
@media (max-width: 768px) {
    header .container {
        flex-direction: column;
        gap: 1rem;
    }

    header ul {
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }

    .hero h2 {
        font-size: 2rem;
    }

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

    .features h2,
    .about h2 {
        font-size: 2rem;
    }

    .feature-grid {
        grid-template-columns: 1fr;
    }

    footer .container {
        flex-direction: column;
        text-align: center;
    }

    footer nav {
        flex-direction: column;
        gap: 1rem;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 2rem;
    }

    .hero {
        padding: 3rem 0;
    }

    .hero h2 {
        font-size: 1.75rem;
    }

    .cta-button {
        padding: 0.875rem 2rem;
        font-size: 1rem;
    }

    .features,
    .about {
        padding: 3rem 0;
    }
}

/* Utility Classes */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: 1rem; }
.mt-2 { margin-top: 2rem; }
.mt-3 { margin-top: 3rem; }

.mb-1 { margin-bottom: 1rem; }
.mb-2 { margin-bottom: 2rem; }
.mb-3 { margin-bottom: 3rem; }

/* Accessibility */
:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Print Styles */
@media print {
    header,
    footer,
    .cta-button {
        display: none;
    }
}