:root { --brand-primary: #1d3b90; --brand-accent: #2f5cc4; --brand-bg: #f8f9fa; --ink: #12203f; }
    * { box-sizing: border-box; }
    body { margin: 0; min-height: 100vh; background: radial-gradient(circle at top left, rgba(47, 92, 196, 0.12), transparent 30%), linear-gradient(180deg, #f4f7fc 0%, var(--brand-bg) 50%, #eef3fb 100%); font-family: system-ui, -apple-system, \"Segoe UI\", sans-serif; color: var(--ink); }
    .container { width: min(1120px, calc(100% - 2rem)); margin: 0 auto; }
    .site-header { position: sticky; top: 0; z-index: 100; background: linear-gradient(90deg, #18357f 0%, #22479f 55%, #1d3b90 100%); color: #fff; box-shadow: 0 10px 24px rgba(13, 27, 61, 0.2); }
    .topbar { display: flex; align-items: center; justify-content: space-between; gap: 1rem; min-height: 96px; padding: 0.75rem 0; }
    .brand { display: inline-flex; align-items: center; gap: 0.75rem; color: #fff; text-decoration: none; letter-spacing: 0.02em; }
    .brand-logo { width: 72px; height: 72px; object-fit: contain; }
    .brand-wordmark { font-size: 1.2rem; font-weight: 700; }
    .header-actions { display: inline-flex; align-items: center; gap: 0.65rem; }
    .lang-switch { display: inline-flex; align-items: center; gap: 0.45rem; }
    .lang-btn { width: 34px; height: 34px; border: 1px solid rgba(255,255,255,0.38); border-radius: 999px; background: rgba(255,255,255,0.12); cursor: pointer; padding: 0; display: inline-flex; align-items: center; justify-content: center; }
    .lang-btn.active { background: #fff; border-color: #fff; }
    .flag-icon { width: 24px; height: 24px; border-radius: 999px; background-position: center; background-repeat: no-repeat; background-size: cover; box-shadow: 0 0 0 1px rgba(17, 34, 68, 0.12), 0 2px 6px rgba(11, 25, 48, 0.18); }
    .lang-btn[data-lang=\"en\"] .flag-icon { background-image: url('/static/assets/images/uk_flag.png'); }
    .lang-btn[data-lang=\"el\"] .flag-icon { background-image: url('/static/assets/images/greece_flag.png'); }
    .hero { padding: 2.2rem 0 1.1rem; }
    .hero-shell { border-radius: 24px; overflow: hidden; color: #fff; background: radial-gradient(circle at 92% 12%, rgba(255, 255, 255, 0.24), transparent 30%), linear-gradient(135deg, rgba(16, 43, 111, 0.95), rgba(47, 92, 196, 0.86)); box-shadow: 0 22px 48px rgba(11, 25, 48, 0.22); padding: 2.2rem; }
    .kicker { margin: 0; font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.16em; font-weight: 700; color: #d5e4ff; }
    .hero-title { margin: 0.55rem 0 0; font-size: clamp(2rem, 4.4vw, 3.35rem); line-height: 1.05; max-width: 12ch; }
    .action-row { margin-top: 1.25rem; display: flex; gap: 0.8rem; flex-wrap: wrap; }
    .surface { padding: 1.2rem 0 2rem; }
    .tree-shell { border: 1px solid rgba(29, 59, 144, 0.1); border-radius: 18px; background: rgba(255, 255, 255, 0.92); backdrop-filter: blur(6px); box-shadow: 0 12px 26px rgba(15, 29, 58, 0.08); padding: 1rem 1.1rem; }
    .tree-title { margin: 0 0 0.65rem; color: #1d3b90; font-size: 1.1rem; }
    .form-tree, .form-tree ul { list-style: none; margin: 0; padding-left: 1rem; }
    .form-tree { padding-left: 0; }
    .tree-item { margin: 0.28rem 0; color: #12203f; }
    .tree-folder > details > summary { cursor: pointer; font-weight: 700; color: #1d3b90; }
    .tree-form { font-weight: 500; }
    .tree-empty { margin: 0; color: #4d5f85; }
    .btn { min-width: 144px; height: 50px; border-radius: 999px; border: 1px solid transparent; font-weight: 700; cursor: pointer; transition: transform 0.16s ease, box-shadow 0.16s ease, background-color 0.16s ease; text-decoration: none; display: inline-flex; align-items: center; justify-content: center; }
    .btn:hover { transform: translateY(-1px); }
    .btn-solid { background: #ffffff; color: var(--brand-primary); box-shadow: 0 8px 18px rgba(9, 22, 52, 0.22); }
    .btn-soft { border-color: rgba(255, 255, 255, 0.4); background: rgba(255, 255, 255, 0.15); color: #fff; }
    .btn-ghost { border-color: rgba(29, 59, 144, 0.2); background: rgba(255, 255, 255, 0.9); color: var(--brand-primary); }
    
    @media (max-width: 900px) { .hero-shell { padding: 1.35rem; } .brand-wordmark { display: none; } }