/* --- VARIABLES & THEME (INDUSTRIAL CARBON) --- */
        :root {
            /* Gris profond et technique */
            --bg-gradient: linear-gradient(135deg, #121212, #2d3436, #1c1c1c);
            --glass-bg: rgba(255, 255, 255, 0.03);
            --glass-border: rgba(255, 255, 255, 0.08);
            
            /* Orange Sécurité pour le contraste */
            --accent-color: #ff5722; 
            --accent-glow: 0 0 15px rgba(255, 87, 34, 0.4);
            
            --text-main: #eceff1;
            --text-muted: #90a4ae; /* Gris bleuté pour adoucir */
            --transition-speed: 0.4s cubic-bezier(0.25, 1, 0.5, 1);
        }

        /* --- RESET --- */
        * { box-sizing: border-box; margin: 0; padding: 0; outline: none; }
        
        body {
            font-family: 'Inter', sans-serif;
            background: var(--bg-gradient);
            color: var(--text-main);
            height: 100vh;
            overflow: hidden;
            display: flex;
            flex-direction: column;
        }

        /* --- HEADER --- */
        header {
            height: 70px;
            display: flex;
            align-items: center;
            padding: 0 25px;
            background: rgba(20, 20, 20, 0.9);
            backdrop-filter: blur(10px);
            border-bottom: 1px solid var(--glass-border);
            position: relative; 
            z-index: 100;
            box-shadow: 0 4px 30px rgba(0, 0, 0, 0.2);
        }

        .brand {
            font-family: 'Rajdhani', sans-serif;
            font-size: 1.5rem;
            letter-spacing: 2px;
            margin-left: 20px;
            text-transform: uppercase;
            background: linear-gradient(to right, #fff, #90a4ae);
            -webkit-background-clip: text;
            background-clip: text;
            -webkit-text-fill-color: transparent;
            color: transparent;
            font-weight: 700;
        }

        /* --- HAMBURGER --- */
        .hamburger {
            cursor: pointer;
            width: 50px;
            height: 50px;
            display: flex;
            justify-content: center;
            align-items: center;
            position: relative;
            z-index: 1000;
            user-select: none; 
            -webkit-tap-highlight-color: transparent;
            margin-left: -10px;
        }

        .hamburger-inner {
            width: 32px;
            height: 24px;
            position: relative;
        }

        .hamburger span {
            display: block;
            position: absolute;
            height: 2px;
            width: 100%;
            background: var(--text-main);
            border-radius: 2px;
            transition: var(--transition-speed);
            left: 0;
            pointer-events: none;
        }

        .hamburger span:nth-child(1) { top: 0px; }
        .hamburger span:nth-child(2) { top: 11px; }
        .hamburger span:nth-child(3) { top: 22px; }

        .hamburger.open span:nth-child(1) { transform: rotate(45deg); top: 11px; background: var(--accent-color); }
        .hamburger.open span:nth-child(2) { opacity: 0; }
        .hamburger.open span:nth-child(3) { transform: rotate(-45deg); top: 11px; background: var(--accent-color); }

        /* --- SIDEBAR --- */
        .sidebar {
            position: absolute;
            top: 0;
            left: 0;
            width: 300px;
            height: 100vh;
            background: rgba(25, 25, 25, 0.98);
            backdrop-filter: blur(15px);
            border-right: 1px solid var(--glass-border);
            transform: translateX(-100%);
            transition: var(--transition-speed);
            z-index: 90;
            padding-top: 90px;
            display: flex;
            flex-direction: column;
        }

        .sidebar.active {
            transform: translateX(0);
            box-shadow: 10px 0 50px rgba(0,0,0,0.5);
        }

        .menu-title {
            padding: 0 25px 8px; /* Réduit en bas (était 15px) pour rapprocher du premier bouton */
            font-size: 1rem;
            text-transform: uppercase;
            color: var(--text-muted);
            letter-spacing: 1px;
            font-weight: 600;
            border-bottom: 1px solid rgba(255,255,255,0.05);
            
            /* C'est ici que ça se joue : */
            margin-top: 45px;    /* Espace MASSIF avant la catégorie (sépare les groupes) */
            margin-bottom: 5px;  /* Espace MINIME après la catégorie (colle au sous-menu) */
        }

        .nav-btn {
            background: transparent;
            border: none;
            color: var(--text-muted);
            padding: 15px 25px;
            width: 100%;
            text-align: left;
            cursor: pointer;
            font-size: 1rem;
            transition: 0.2s;
            position: relative;
            font-family: 'Rajdhani', sans-serif;
            letter-spacing: 1px;

            /* MODIFICATION ICI : Ajout d'une marge sous chaque bouton */
            margin-bottom: 8px; 
        }

        .nav-btn::before {
            content: '';
            position: absolute;
            left: 0;
            top: 0;
            height: 100%;
            width: 3px;
            background: var(--accent-color);
            transform: scaleY(0);
            transition: transform 0.2s;
        }

        .nav-btn:hover {
            color: #fff;
            background: rgba(255,255,255,0.03);
        }

        .nav-btn:hover::before, .nav-btn.active::before {
            transform: scaleY(1);
        }

        .nav-btn.active {
            color: var(--accent-color);
            background: linear-gradient(90deg, rgba(255, 87, 34, 0.08), transparent);
            text-shadow: var(--accent-glow);
        }

        /* --- MAIN AREA & IFRAME --- */
        main {
            flex-grow: 1;
            position: relative;
            background: radial-gradient(circle at center, #2d3436 0%, #121212 100%);
            display: flex;
            align-items: center;
            justify-content: center;
        }

        iframe {
            width: 100%;
            height: 100%;
            border: none;
            display: block;
            opacity: 0;
            transition: opacity 0.5s ease;
        }
        
        iframe.loaded {
            opacity: 1;
        }

        .overlay {
            position: fixed;
            top: 0; left: 0; right: 0; bottom: 0;
            background: rgba(0,0,0,0.7);
            backdrop-filter: blur(3px);
            z-index: 80;
            opacity: 0;
            pointer-events: none;
            transition: opacity var(--transition-speed);
        }

        .overlay.active {
            opacity: 1;
            pointer-events: auto;
        }