/* ===== GLOBAL STYLES & VARIABLES ===== */
:root {
    --primary-color: #2c3e50; /* Koyu Lacivert */
    --secondary-color: #3498db; /* Vurgu Rengi - Açık Mavi */
    --background-light: #f8f9fa;
    --text-dark: #343a40;
    --text-light: #6c757d;
    --white-color: #ffffff;
    --border-color: #dee2e6;
    --font-primary: 'Montserrat', sans-serif;
    --font-secondary: 'Roboto', sans-serif;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-secondary);
    color: var(--text-dark);
    line-height: 1.7;
    /* Set the background image for the entire page */
    background-image: url('background.jpg');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
}

.container {
    max-width: 1140px;
    margin: 0 auto;
    padding: 0 20px;
}

.section {
    padding: 80px 0;
    background-color: rgba(255, 255, 255, 0.9); /* Semi-transparent white background */
}

/* Sayfa kaydırıldıkça beliren animasyon için stil */
.section.hidden {
    opacity: 0;
    transform: translateY(50px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.section-title {
    font-family: var(--font-primary);
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 4rem;
    color: var(--primary-color);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -15px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background-color: var(--secondary-color);
}

.bg-light {
    background-color: rgba(248, 249, 250, 0.95); /* Slightly more opaque for contrast */
}

/* ===== NAVIGATION BAR ===== */
.navbar {
    background-color: transparent;
    padding: 1rem 0;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    transition: background-color 0.4s ease, padding 0.4s ease;
}

.navbar .container {
    display: flex;
    justify-content: center;
    align-items: center;
}

.nav-menu {
    list-style: none;
    display: flex;
    gap: 1.5rem;
}

.nav-menu a {
    color: var(--white-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.4s ease;
}

.nav-menu a:hover {
    color: var(--secondary-color);
}

.navbar.scrolled {
    background-color: var(--white-color);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    padding: 0.75rem 0;
}

.navbar.scrolled .nav-menu a {
    color: var(--primary-color);
}

.navbar.scrolled .nav-menu a:hover,
.nav-menu a.active {
    color: var(--secondary-color);
    font-weight: 700;
}

/* ===== HERO SECTION ===== */
.hero {
    background: linear-gradient(rgba(44, 62, 80, 0.85), rgba(44, 62, 80, 0.85)), url('https://images.unsplash.com/photo-1507413245164-6160d8298b31?q=80&w=2070') no-repeat center center/cover;
    color: var(--white-color);
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.hero-title {
    font-family: var(--font-primary);
    font-size: 4rem;
    font-weight: 700;
}

.hero-subtitle {
    font-size: 1.5rem;
    margin: 1rem 0 2rem;
    font-weight: 400;
}

.hero-contact {
    margin-top: 1.5rem;
    display: flex;
    gap: 1.5rem;
    justify-content: center;
    font-size: 0.9rem;
}

.btn {
    padding: 12px 30px;
    border-radius: 5px;
    display: inline-block; /* Dikey margin'lerin uygulanabilmesi için eklendi */
    text-decoration: none;
    font-weight: 700;
    transition: all 0.3s;
}

.btn-primary {
    background-color: var(--secondary-color);
    color: var(--white-color);
    margin-top: 2rem; /* Butonu aşağı çekmek için boşluk eklendi */
}

.btn-primary:hover {
    color: var(--white-color);
    background-color: #2980b9; /* Darker blue */
    transform: translateY(-2px);
}

/* ===== CARD STYLES (for Experience & Education) ===== */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.card {
    background-color: var(--white-color);
    padding: 2rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.1);
}

.card-title {
    font-family: var(--font-primary);
    color: var(--primary-color);
    font-size: 1.3rem;
}

.card-subtitle {
    color: var(--text-light);
    font-weight: 500;
    margin: 0.5rem 0;
}

.card-date {
    color: var(--secondary-color);
    font-weight: 700;
    margin-bottom: 1rem;
}

/* ===== PUBLICATIONS SECTION ===== */
.publication-list {
    list-style: decimal;
    padding-left: 20px;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.publication-list li {
    padding-left: 10px;
}

/* ===== SKILLS SECTION ===== */
.skills-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    text-align: center;
}

.skill-category h3 {
    font-family: var(--font-primary);
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.skill-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
}

.skill-item {
    background-color: var(--background-light);
    color: var(--text-dark);
    padding: 8px 15px;
    border-radius: 20px;
    border: 1px solid var(--border-color);
    font-weight: 500;
}

/* ===== FOOTER & CONTACT ===== */
.footer {
    background-color: var(--primary-color);
    color: var(--white-color);
    text-align: center;
    padding: 2rem 0;
}

#contact p {
    max-width: 600px;
    margin: -2rem auto 2rem auto;
    text-align: center;
}

.contact-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.contact-link {
    color: var(--text-dark);
    text-decoration: none;
    font-size: 1.1rem;
    transition: color 0.3s;
    font-weight: 500;
}

.contact-link:hover {
    color: var(--secondary-color);
}

.copyright {
    color: rgba(255, 255, 255, 0.7);
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 768px) {
    .hero-title {
        font-size: 3rem;
    }
    .hero-subtitle {
        font-size: 1.2rem;
    }
    .hero-contact {
        flex-direction: column;
        gap: 0.5rem;
    }
    .nav-menu {
        display: none; /* Mobil için menüyü gizle (geliştirilebilir) */
    }
    .skills-wrapper {
        grid-template-columns: 1fr;
    }
}