/* --- DEĞİŞKENLER (RENK PALETİ: SARI - KIRMIZI) --- */
        :root {
            /* --- DARK MODE (VARSAYILAN) --- */
            --primary-red: #E30613;       /* Galatasaray Kırmızısı */
            --accent-yellow: #FDB912;     /* Galatasaray Sarısı */
            
            --bg-color: #0a0a0a;
            --card-bg: #161b22;
            --text-color: #ffffff;
            --text-secondary: #b0b0b0;
            --header-bg: rgba(10, 10, 10, 0.95);
            --border-color: #333;
            --hero-overlay: rgba(0,0,0,0.8);
            --form-input-bg: #0f1318;
        }

        /* --- LIGHT MODE RENKLERİ --- */
        body.light-mode {
            --primary-red: #b00000;
            --accent-yellow: #d49b00;
            
            --bg-color: #f4f4f9;
            --card-bg: #ffffff;
            --text-color: #333333;
            --text-secondary: #555555;
            --header-bg: rgba(255, 255, 255, 0.95);
            --border-color: #ddd;
            --hero-overlay: rgba(0,0,0,0.6);
            --form-input-bg: #f9f9f9;
        }

        /* GENEL AYARLAR */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            text-decoration: none;
            list-style: none;
        }

        body {
            font-family: 'Poppins', sans-serif;
            background-color: var(--bg-color);
            color: var(--text-color);
            line-height: 1.6;
            scroll-behavior: smooth;
            transition: background-color 0.3s, color 0.3s;
        }

        .container {
            max-width: 1100px;
            margin: 0 auto;
            padding: 0 20px;
        }

        /* HEADER / MENÜ */
        header {
            background-color: var(--header-bg);
            padding: 20px 0;
            position: fixed;
            width: 100%;
            top: 0;
            z-index: 1000;
            border-bottom: 2px solid var(--primary-red);
            transition: background-color 0.3s;
        }

        nav {
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .logo {
            font-size: 1.5rem;
            font-weight: 700;
            color: var(--text-color);
        }

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

        .nav-links {
            display: flex;
            gap: 30px;
        }

        .nav-links a {
            color: var(--text-color);
            font-weight: 500;
            font-size: 0.95rem;
            transition: color 0.3s;
        }

        .nav-links a:hover {
            color: var(--primary-red);
        }

        .theme-toggle {
            background: var(--primary-red);
            border: 2px solid var(--accent-yellow);
            width: 35px;
            height: 35px;
            border-radius: 50%;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--accent-yellow);
            font-size: 1.1rem;
            transition: transform 0.2s;
        }
        
        .theme-toggle:hover {
            transform: scale(1.1);
        }

        /* HERO SECTION */
        .hero {
            height: 100vh;
            background: linear-gradient(var(--hero-overlay), var(--hero-overlay)), url('https://images.unsplash.com/photo-1562774053-701939374585?q=80&w=1920&auto=format&fit=crop'); 
            background-size: cover;
            background-position: center;
            display: flex;
            align-items: center;
            justify-content: center;
            text-align: center;
            padding-top: 60px;
            color: #fff;
        }

        .hero-content h1 {
            font-size: 3.5rem;
            margin-bottom: 10px;
        }

        .hero-content h1 span {
            color: var(--accent-yellow);
            text-shadow: 2px 2px 0px rgba(0,0,0,0.5);
        }

        .subtitle {
            font-size: 1.2rem;
            color: #e0e0e0;
            margin-bottom: 30px;
            font-weight: 300;
        }

        /* STANDART KIRMIZI BUTON */
        .btn {
            display: inline-block;
            background-color: var(--primary-red);
            color: #fff;
            padding: 12px 30px;
            border-radius: 50px;
            font-weight: 600;
            transition: transform 0.3s, box-shadow 0.3s, background-color 0.3s;
            border: 1px solid var(--accent-yellow);
            cursor: pointer;
        }

        .btn:hover {
            transform: translateY(-3px);
            box-shadow: 0 0 15px rgba(253, 185, 18, 0.4);
            background-color: #c2000b;
        }
        
        /* YENİ SARI BUTON (ADÜ İÇİN) */
        .btn-yellow {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            background-color: var(--accent-yellow);
            color: #222; /* Sarı üstüne koyu yazı */
            padding: 10px 25px;
            border-radius: 50px;
            font-weight: 700;
            margin-top: 25px;
            transition: all 0.3s ease;
            border: 2px solid var(--accent-yellow);
            font-size: 0.9rem;
        }

        .btn-yellow:hover {
            background-color: transparent;
            color: var(--accent-yellow);
            box-shadow: 0 0 15px rgba(253, 185, 18, 0.3);
            transform: translateY(-2px);
        }

        /* BÖLÜM BAŞLIKLARI */
        .section-title {
            color: var(--primary-red);
            font-size: 1.8rem;
            margin-bottom: 20px;
            position: relative;
            display: inline-block;
        }
        
        .section-title::after {
            content: '';
            display: block;
            width: 50%;
            height: 3px;
            background: var(--accent-yellow);
            margin-top: 5px;
            border-radius: 2px;
        }

        section {
            padding: 80px 0;
        }

        /* HAKKIMDA */
        #hakkimda p {
            color: var(--text-secondary);
            font-size: 1.1rem;
            max-width: 800px;
        }

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

        .card {
            background-color: var(--card-bg);
            padding: 30px;
            border-radius: 12px;
            transition: transform 0.3s, border-color 0.3s;
            border: 1px solid var(--border-color);
            box-shadow: 0 4px 6px rgba(0,0,0,0.05);
            position: relative;
            overflow: hidden;
        }
        
        .card::before {
            content: '';
            position: absolute;
            top: 0; left: 0; width: 100%; height: 3px;
            background: var(--accent-yellow);
            transform: scaleX(0);
            transform-origin: left;
            transition: transform 0.3s;
        }

        .card:hover {
            transform: translateY(-10px);
            border-color: var(--primary-red);
        }
        
        .card:hover::before {
            transform: scaleX(1);
        }

        .card h3 {
            margin-bottom: 15px;
            font-size: 1.4rem;
            color: var(--text-color);
        }

        .card p {
            color: var(--text-secondary);
            font-size: 0.95rem;
        }

        /* --- YENİ KAYIT OL FORMU BÖLÜMÜ --- */
        .kayit-section {
            background-color: rgba(0,0,0,0.2); /* Biraz daha koyu bir ton */
        }
        body.light-mode .kayit-section {
             background-color: #eaeaf0;
        }

        .form-container {
            max-width: 550px;
            margin: 40px auto 0;
            background-color: var(--card-bg);
            padding: 40px;
            border-radius: 15px;
            border: 1px solid var(--border-color);
            box-shadow: 0 15px 35px rgba(0,0,0,0.2);
            position: relative;
            overflow: hidden;
        }
        /* Formun tepesine sarı-kırmızı gradient çizgi */
        .form-container::before {
            content: '';
            position: absolute;
            top: 0; left: 0; width: 100%; height: 5px;
            background: linear-gradient(to right, var(--primary-red), var(--accent-yellow));
        }

        .input-group {
            position: relative;
            margin-bottom: 35px;
        }

        .input-group input {
            width: 100%;
            padding: 15px 15px 15px 45px; /* İkon için soldan boşluk */
            background-color: var(--form-input-bg);
            border: 2px solid var(--border-color);
            border-radius: 8px;
            color: var(--text-color);
            font-family: inherit;
            font-size: 1rem;
            outline: none;
            transition: all 0.3s;
        }

        .input-group input:focus,
        .input-group input:valid {
            border-color: var(--accent-yellow);
            background-color: var(--card-bg);
        }

        .input-group label {
            position: absolute;
            top: 50%;
            left: 45px;
            transform: translateY(-50%);
            color: var(--text-secondary);
            pointer-events: none;
            transition: all 0.3s ease;
        }
        
        .input-group .icon {
            position: absolute;
            top: 50%;
            left: 15px;
            transform: translateY(-50%);
            color: var(--primary-red);
            font-size: 1.1rem;
            transition: all 0.3s;
        }

        /* Floating Label Efekti */
        .input-group input:focus ~ label,
        .input-group input:valid ~ label {
            top: -12px;
            left: 10px;
            font-size: 0.85rem;
            background-color: var(--card-bg);
            padding: 0 8px;
            color: var(--accent-yellow);
            font-weight: 600;
        }
        
        .input-group input:focus ~ .icon,
        .input-group input:valid ~ .icon {
             color: var(--accent-yellow);
        }

        .form-btn {
            width: 100%;
            font-size: 1.1rem;
            padding: 15px;
        }

        /* İLETİŞİM VE FOOTER */
        #iletisim {
            padding-bottom: 40px;
        }

        .contact-links {
            margin-top: 20px;
        }

        .contact-item {
            display: flex;
            align-items: center;
            gap: 10px;
            margin-bottom: 15px;
            color: var(--primary-red);
        }
        
        .contact-item i {
            color: var(--accent-yellow);
            font-size: 1.2rem;
        }
        
        .contact-item a {
            color: var(--text-color);
            transition: color 0.3s;
        }
        
        .contact-item a:hover {
            color: var(--primary-red);
        }

        footer {
            text-align: center;
            padding: 20px;
            border-top: 1px solid var(--border-color);
            color: var(--text-secondary);
            font-size: 0.9rem;
            background-color: var(--bg-color);
        }

        /* RESPONSIVE */
        @media (max-width: 768px) {
            .hero-content h1 { font-size: 2.5rem; }
            .nav-links { display: none; } 
            .form-container { padding: 30px 20px; }
        }
        html {
            scroll-behavior: smooth;
        }