/* Custom properties for a sleek, dark-themed, professional look */
:root {
  --primary-color: #0d1117; /* Very Dark Background (GitHub style) */
  --secondary-color: #161b22; /* Slightly Lighter Background for sections */
  --accent-color: #0ea5e9; /* Sky Blue for links/buttons */
  --accent-soft: #38bdf8; /* Lighter accent */
  --text-light: #f0f6fc; /* Off-White for body text */
  --text-dark: #8b949e; /* Gray for subtle text/details */
  --font-family: 'Inter', sans-serif;
  --transition-speed: 0.5s;
  --max-width: 1200px;
}

/* Global Reset and Base Styling */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  line-height: 1.6;
  color: var(--text-dark);
  background-color: var(--primary-color);
  padding-top: 80px; /* Space for the fixed header */
}

/* Base Utility Classes */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 5%;
}

.section {
  padding: 80px 0;
  overflow: hidden; /* Important for animations */
}

/* Typography */
h1, h2, h3 {
  color: var(--text-light);
  line-height: 1.2;
  margin-bottom: 20px;
  font-weight: 700;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.5rem; border-bottom: 2px solid var(--secondary-color); padding-bottom: 10px; }
h3 { font-size: 1.75rem; }

p {
  margin-bottom: 15px;
}

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

a:hover {
  color: var(--accent-soft);
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 30px;
  background-color: var(--accent-color);
  color: var(--primary-color);
  border-radius: 8px;
  font-weight: 600;
  transition: all var(--transition-speed);
  box-shadow: 0 4px 15px rgba(14, 165, 233, 0.4);
}

.btn:hover {
  background-color: var(--accent-soft);
  color: var(--primary-color);
  box-shadow: 0 6px 20px rgba(56, 189, 248, 0.6);
  transform: translateY(-2px);
}

/* --- Header & Navigation --- */

header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background-color: var(--primary-color);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.5);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 5%;
  height: 80px;
}

.logo a {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--text-light);
}

.logo span {
  color: var(--accent-color);
}

.navbar ul {
  display: flex;
  list-style: none;
}

.navbar li {
  margin-left: 30px;
}

.navbar a {
  color: var(--text-light);
  font-weight: 500;
  padding: 5px 0;
  position: relative;
}

.navbar a:hover,
.navbar a.active {
  color: var(--accent-soft);
}

/* Underline animation for professionalism */
.navbar a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0%;
  height: 2px;
  background-color: var(--accent-soft);
  transition: width 0.3s ease;
}

.navbar a:hover::after,
.navbar a.active::after {
  width: 100%;
}

.nav-toggle {
  display: none; /* Hide on desktop */
  background: none;
  border: none;
  color: var(--text-light);
  font-size: 1.5rem;
  cursor: pointer;
  transition: color 0.3s;
}

.nav-toggle:hover {
  color: var(--accent-color);
}

/* --- Hero Section Styling (Headers with Backgrounds) --- */

.hero-section {
    min-height: 40vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    background-size: cover;
    background-position: center;
    transition: background-image 1s ease-in-out;
}

.hero-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    /* Dark overlay for contrast and professionalism */
    background: linear-gradient(135deg, rgba(13, 17, 23, 0.9) 0%, rgba(22, 27, 34, 0.7) 100%);
    z-index: 1;
}

.hero-section .container {
    position: relative;
    z-index: 2;
    padding: 40px 5%;
}

.hero-section h1 {
    font-size: 3.5rem;
    margin-bottom: 15px;
    text-shadow: 0 0 10px rgba(0, 0, 0, 0.8);
}

.hero-section p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto 30px;
    color: var(--text-dark);
}

/* Individual Hero Backgrounds (Using gradient/noise patterns as placeholders) */

/* Home Page: AI/Biotech Fusion */
.hero-home {
    /* background-image: url('https://placehold.co/1920x600/1e293b/38bdf8?text=Precision+AI+Intelligence'); */
    background-image: url('https://www.mouser.com/blog/Portals/11/Cassar_Hottest%20Thing%20in%20AI_Theme%20Image.jpg');
    background-attachment: fixed;
    background-size: cover;
}

/* Vaxi-DL: Deep Learning for Vaccines */
.hero-vaxidl {
    background-image: url('https://placehold.co/1920x600/1e293b/0ea5e9?text=Deep+Learning+Pipeline+Visualization');
}

/* Vax-Elan: Explainable AI */
.hero-vaxelan {
    background-image: url('https://placehold.co/1920x600/161b22/f0f6fc?text=Explainable+AI+Mechanism');
}

/* Neoantigen.ai: Personalized Immunotherapy */
.hero-neoantigen {
    background-image: url('https://placehold.co/1920x600/0d1117/38bdf8?text=Cancer+Targeting+Molecular+Structure');
}

/* Contact Page: Connection */
.hero-contact {
    background-image: url('https://placehold.co/1920x600/161b22/0ea5e9?text=Global+Collaboration+Network');
}

/* --- Section Content Styling --- */

/* Feature Grid */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.feature-card {
    background-color: var(--secondary-color);
    padding: 30px;
    border-radius: 12px;
    text-align: center;
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    border: 1px solid var(--secondary-color);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.4), 0 0 15px var(--accent-color);
    border-color: var(--accent-color);
}

.feature-card i {
    font-size: 3rem;
    color: var(--accent-color);
    margin-bottom: 15px;
}

.feature-card h3 {
    margin-bottom: 10px;
    color: var(--text-light);
}

/* Split Content (Text/Image blocks) */
.split-content {
    display: flex;
    align-items: center;
    gap: 50px;
    margin-bottom: 60px;
}

.split-content > div {
    flex: 1;
}

.split-content img {
    max-width: 100%;
    height: auto;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

.split-content.reverse {
    flex-direction: row-reverse;
}

/* --- Contact Section / Form --- */
.contact-form-container {
    background-color: var(--secondary-color);
    padding: 40px;
    border-radius: 12px;
    max-width: 600px;
    margin: 40px auto;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.contact-form label {
    display: block;
    margin-top: 15px;
    margin-bottom: 5px;
    color: var(--text-light);
    font-weight: 500;
}

.contact-form input[type="text"],
.contact-form input[type="email"],
.contact-form textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid #333;
    background-color: #0d1117;
    color: var(--text-light);
    border-radius: 6px;
    transition: border-color 0.3s;
}

.contact-form input:focus,
.contact-form textarea:focus {
    border-color: var(--accent-color);
    outline: none;
    box-shadow: 0 0 0 2px rgba(14, 165, 233, 0.5);
}

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

.contact-form button {
    width: 100%;
    margin-top: 20px;
}

#formStatus {
    margin-top: 20px;
    text-align: center;
    color: #4ade80; /* Success green */
    font-weight: 600;
}

/* --- Footer --- */
footer {
    background-color: var(--secondary-color);
    padding: 60px 0 20px;
    border-top: 5px solid var(--accent-color); /* Stronger separator */
}

.footer-content {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 30px;
}

.footer-col {
    flex: 1 1 200px;
    min-width: 150px;
}

.footer-col h4 {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 20px;
    position: relative;
}

.footer-col h4::after {
    content: '';
    position: absolute;
    left: 0;
    bottom: -5px;
    height: 2px;
    width: 50px;
    background-color: var(--accent-color);
}

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

.footer-col ul li:not(:last-child) {
    margin-bottom: 10px;
}

.footer-col ul li a {
    color: var(--text-dark);
    display: block;
    transition: color 0.3s, transform 0.3s;
}

.footer-col ul li a:hover {
    color: var(--accent-soft);
    padding-left: 5px;
}

.social-links a {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    height: 40px;
    width: 40px;
    background-color: rgba(255, 255, 255, 0.05);
    margin: 0 10px 10px 0;
    text-align: center;
    line-height: 40px;
    border-radius: 50%;
    color: var(--text-light);
    transition: all 0.5s ease;
}

.social-links a:hover {
    color: var(--primary-color);
    background-color: var(--accent-color);
    transform: rotate(360deg) scale(1.1);
}

.footer-bottom {
    text-align: center;
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid rgba(139, 148, 158, 0.1);
    font-size: 0.9rem;
}

.footer-bottom p {
    color: var(--text-dark);
    margin: 0;
}

/* --- Scroll Animation Styles (Opacity and Slide-Up) --- */

.section {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 1s ease-out, transform 0.8s ease-out;
}

.section.visible {
    opacity: 1;
    transform: translateY(0);
}

/* --- Responsive Design --- */

@media (max-width: 900px) {
    header {
        padding: 15px 5%;
    }
    
    .navbar {
        display: none;
        flex-direction: column;
        width: 100%;
        position: absolute;
        top: 80px;
        left: 0;
        background-color: var(--secondary-color);
        box-shadow: 0 5px 15px rgba(0, 0, 0, 0.5);
    }

    .navbar.open {
        display: flex;
    }

    .navbar ul {
        flex-direction: column;
        padding: 20px 0;
        width: 100%;
    }

    .navbar li {
        margin: 0;
        text-align: center;
        border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    }
    
    .navbar li:last-child {
        border-bottom: none;
    }

    .navbar a {
        display: block;
        padding: 15px 0;
        font-size: 1.1rem;
    }

    .nav-toggle {
        display: block;
    }

    h1 { font-size: 2.5rem; }
    h2 { font-size: 2rem; }
    
    .hero-section h1 {
        font-size: 2.8rem;
    }

    .split-content {
        flex-direction: column;
        text-align: center;
    }

    .split-content.reverse {
        flex-direction: column;
    }

    .split-content-image {
        order: -1; /* Move image above text on mobile for reverse layout */
        margin-bottom: 30px;
    }

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

    .footer-col {
        margin-bottom: 20px;
        width: 100%;
    }
    
    .footer-col h4::after {
        left: 50%;
        transform: translateX(-50%);
    }

    .footer-col ul {
        padding-left: 0;
    }
    
    .social-links {
        justify-content: center;
        display: flex;
    }
}