:root {
    --bg: #05070d;
    --bg-2: #0a0f1c;
    --card: rgba(12, 18, 34, 0.8);
    --card-hover: rgba(20, 30, 55, 0.92);
    --border: rgba(0, 212, 255, 0.18);
    --border-hover: rgba(0, 212, 255, 0.6);
    --text: #e8edf6;
    --muted: #7d8aa0;
    --accent: #00d4ff;      /* ciano neon */
    --accent-2: #7c3aed;    /* viola */
    --accent-3: #ff2d95;    /* rosa neon */
    --red: #ff2d2d;         /* rosso allarme */
    --green: #00ff88;       /* verde matrix */
    --yellow: #ffb800;      /* oro/ambra */
    --glow-cyan: 0 0 20px rgba(0, 212, 255, 0.4);
    --glow-red: 0 0 20px rgba(255, 45, 45, 0.4);
}

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

body {
    font-family: 'Share Tech Mono', 'Courier New', monospace;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    position: relative;
    overflow-x: hidden;
}

/* ===== Matrix rain canvas ===== */
#matrix-rain {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    opacity: 0.35;
    pointer-events: none;
}

/* ===== Sfondo base ===== */
body::before {
    content: '';
    position: fixed;
    inset: 0;
    z-index: -2;
    background:
        radial-gradient(ellipse at 20% 0%, rgba(124, 58, 237, 0.18) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 10%, rgba(0, 212, 255, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 100%, rgba(255, 45, 45, 0.1) 0%, transparent 50%),
        var(--bg);
}

/* ===== Font titoli ===== */
h1, h2, h3, .brand, .stat .num, .page-title {
    font-family: 'Orbitron', 'Share Tech Mono', sans-serif;
    letter-spacing: 1px;
}

/* ===== Navbar ===== */
.navbar {
    background: rgba(5, 7, 13, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
}
.nav-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 14px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.brand {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--text);
    text-decoration: none;
    letter-spacing: 2px;
    display: flex;
    align-items: center;
    gap: 10px;
    text-transform: uppercase;
}
.brand .logo {
    font-size: 1.6rem;
    filter: drop-shadow(0 0 10px rgba(0, 212, 255, 0.8));
    animation: pulse 2s ease-in-out infinite;
}
@keyframes pulse {
    0%, 100% { transform: scale(1); filter: drop-shadow(0 0 8px rgba(0,212,255,0.6)); }
    50% { transform: scale(1.08); filter: drop-shadow(0 0 18px rgba(0,212,255,1)); }
}
.brand span {
    background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 0 30px rgba(0, 212, 255, 0.3);
}
.nav-links { display: flex; gap: 28px; align-items: center; }
.nav-links a {
    color: var(--muted);
    text-decoration: none;
    font-size: 0.95rem;
    transition: all 0.2s;
    position: relative;
    text-transform: uppercase;
    letter-spacing: 1px;
}
.nav-links a:hover, .nav-links a.active { color: var(--accent); text-shadow: 0 0 10px rgba(0, 212, 255, 0.6); }
.nav-links a.active::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--accent);
    box-shadow: var(--glow-cyan);
}
.nav-links a.btn-auth {
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    color: #fff;
    padding: 9px 20px;
    border-radius: 6px;
    font-weight: 700;
    box-shadow: var(--glow-cyan);
    clip-path: polygon(8px 0, 100% 0, 100% calc(100% - 8px), calc(100% - 8px) 100%, 0 100%, 0 8px);
}
.nav-links a.btn-auth:hover { transform: translateY(-1px); box-shadow: 0 0 30px rgba(0, 212, 255, 0.6); }

/* ===== Hero ===== */
.hero {
    text-align: center;
    padding: 80px 24px 50px;
    position: relative;
}
.hero h1 {
    font-size: 3.2rem;
    margin-bottom: 18px;
    background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    filter: drop-shadow(0 0 30px rgba(0, 212, 255, 0.4));
    letter-spacing: 3px;
    text-transform: uppercase;
}
.hero p {
    color: var(--muted);
    max-width: 640px;
    margin: 0 auto 30px;
    font-size: 1.05rem;
    line-height: 1.7;
}
.hero-stats { display: flex; gap: 50px; justify-content: center; flex-wrap: wrap; }
.stat {
    text-align: center;
    padding: 18px 30px;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 8px;
    backdrop-filter: blur(8px);
    position: relative;
    clip-path: polygon(12px 0, 100% 0, 100% calc(100% - 12px), calc(100% - 12px) 100%, 0 100%, 0 12px);
}
.stat::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--accent), var(--accent-3));
    opacity: 0.6;
}
.stat .num {
    font-size: 2.2rem;
    font-weight: 800;
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 0 20px rgba(0, 212, 255, 0.3);
}
.stat .lbl { color: var(--muted); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 2px; margin-top: 4px; }

/* ===== Container ===== */
.container { max-width: 1200px; margin: 0 auto; padding: 30px 24px; flex: 1; width: 100%; }
.page-title {
    font-size: 2rem;
    margin-bottom: 28px;
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-transform: uppercase;
    letter-spacing: 2px;
}

/* ===== Filtri ===== */
.filters { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 28px; }
.filter-btn {
    background: var(--card);
    color: var(--muted);
    border: 1px solid var(--border);
    padding: 9px 18px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s;
    backdrop-filter: blur(8px);
    text-transform: uppercase;
    letter-spacing: 1px;
    font-family: 'Share Tech Mono', monospace;
}
.filter-btn:hover { border-color: var(--accent); color: var(--text); transform: translateY(-1px); box-shadow: var(--glow-cyan); }
.filter-btn.active {
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    color: #fff;
    border-color: transparent;
    font-weight: 700;
    box-shadow: var(--glow-cyan);
}

/* ===== Griglia sfide ===== */
.challenges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}
.challenge-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
    cursor: pointer;
    transition: all 0.25s;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(8px);
    clip-path: polygon(14px 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%, 0 14px);
}
.challenge-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
    opacity: 0;
    transition: opacity 0.25s;
}
.challenge-card::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: linear-gradient(45deg, transparent 40%, rgba(0, 212, 255, 0.05) 50%, transparent 60%);
    transform: translateX(-100%);
    transition: transform 0.6s;
    pointer-events: none;
}
.challenge-card:hover {
    background: var(--card-hover);
    transform: translateY(-4px);
    border-color: var(--border-hover);
    box-shadow: 0 8px 40px rgba(0, 212, 255, 0.2);
}
.challenge-card:hover::before { opacity: 1; }
.challenge-card:hover::after { transform: translateX(100%); }
.challenge-card .cat {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.75rem;
    color: var(--accent);
    margin-bottom: 12px;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    font-weight: 600;
}
.challenge-card h3 { font-size: 1.15rem; margin-bottom: 8px; text-transform: uppercase; letter-spacing: 1px; }
.challenge-card .desc {
    color: var(--muted);
    font-size: 0.9rem;
    margin-bottom: 16px;
    line-height: 1.5;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}
.challenge-card .meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
    gap: 8px;
    flex-wrap: wrap;
}
.challenge-card .points {
    background: linear-gradient(90deg, var(--accent-2), var(--accent-3));
    color: #fff;
    padding: 5px 14px;
    border-radius: 4px;
    font-weight: 700;
    box-shadow: 0 0 15px rgba(124, 58, 237, 0.4);
    clip-path: polygon(6px 0, 100% 0, 100% calc(100% - 6px), calc(100% - 6px) 100%, 0 100%, 0 6px);
}
.challenge-card .solves { color: var(--muted); }
.diff { font-size: 0.7rem; padding: 3px 10px; border-radius: 3px; font-weight: 700; text-transform: uppercase; letter-spacing: 1px; }
.diff.easy { background: rgba(0,255,136,0.12); color: var(--green); border: 1px solid rgba(0,255,136,0.3); }
.diff.medium { background: rgba(255,184,0,0.12); color: var(--yellow); border: 1px solid rgba(255,184,0,0.3); }
.diff.hard { background: rgba(255,45,45,0.12); color: var(--red); border: 1px solid rgba(255,45,45,0.3); }
.diff.expert { background: rgba(124,58,237,0.2); color: #a78bfa; border: 1px solid rgba(124,58,237,0.4); }
.solved-badge {
    position: absolute;
    top: 14px;
    right: 14px;
    color: var(--green);
    font-size: 1.3rem;
    filter: drop-shadow(0 0 8px rgba(0,255,136,0.6));
}

/* ===== Modale ===== */
.modal {
    position: fixed;
    inset: 0;
    background: rgba(3, 5, 10, 0.85);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
    padding: 20px;
    animation: fadeIn 0.2s ease;
}
.modal.hidden { display: none; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
.modal-content {
    background: linear-gradient(160deg, #0d1526, #080d18);
    border: 1px solid var(--border);
    border-radius: 12px;
    max-width: 660px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    padding: 34px;
    position: relative;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.7), 0 0 50px rgba(0, 212, 255, 0.15);
    animation: slideUp 0.25s ease;
    clip-path: polygon(16px 0, 100% 0, 100% calc(100% - 16px), calc(100% - 16px) 100%, 0 100%, 0 16px);
}
@keyframes slideUp { from { transform: translateY(20px); opacity: 0; } to { transform: translateY(0); opacity: 1; } }
.modal-close {
    position: absolute;
    top: 16px;
    right: 16px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border);
    color: var(--muted);
    width: 36px;
    height: 36px;
    border-radius: 6px;
    font-size: 1.1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    line-height: 1;
    font-family: 'Share Tech Mono', monospace;
}
.modal-close:hover { background: rgba(255, 45, 45, 0.2); color: var(--red); border-color: var(--red); transform: rotate(90deg); box-shadow: var(--glow-red); }
.modal-content h2 { font-size: 1.6rem; margin-bottom: 8px; padding-right: 40px; text-transform: uppercase; letter-spacing: 1px; }
.modal-content .cat { color: var(--accent); font-size: 0.85rem; margin-bottom: 18px; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; text-transform: uppercase; letter-spacing: 1px; }
.modal-content .desc {
    color: var(--text);
    line-height: 1.7;
    margin-bottom: 18px;
    white-space: pre-wrap;
    background: rgba(0, 212, 255, 0.03);
    border: 1px solid rgba(0, 212, 255, 0.1);
    border-radius: 8px;
    padding: 18px;
    font-size: 0.95rem;
}
.modal-content .hint {
    background: rgba(255, 184, 0, 0.08);
    border-left: 3px solid var(--yellow);
    padding: 12px 16px;
    border-radius: 6px;
    color: var(--yellow);
    margin-bottom: 20px;
    font-size: 0.9rem;
    line-height: 1.5;
}
.modal-content .points-big {
    font-size: 1.2rem;
    font-weight: 800;
    background: linear-gradient(90deg, var(--accent-2), var(--accent-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 20px;
}
.flag-form { display: flex; gap: 10px; }
.flag-form input {
    flex: 1;
    background: rgba(3, 5, 10, 0.8);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 13px 16px;
    border-radius: 6px;
    font-size: 0.95rem;
    font-family: 'Share Tech Mono', monospace;
    transition: border-color 0.2s;
}
.flag-form input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px rgba(0, 212, 255, 0.15), var(--glow-cyan); }
.flag-result { margin-top: 14px; padding: 12px 16px; border-radius: 6px; font-size: 0.9rem; animation: fadeIn 0.2s ease; }
.flag-result.success { background: rgba(0,255,136,0.1); color: var(--green); border: 1px solid rgba(0,255,136,0.3); }
.flag-result.error { background: rgba(255,45,45,0.1); color: var(--red); border: 1px solid rgba(255,45,45,0.3); }
.flag-result.info { background: rgba(0,212,255,0.1); color: var(--accent); border: 1px solid rgba(0,212,255,0.3); }

/* ===== Bottoni ===== */
.btn {
    background: var(--card);
    color: var(--text);
    border: 1px solid var(--border);
    padding: 11px 22px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.95rem;
    transition: all 0.2s;
    font-family: 'Share Tech Mono', monospace;
    text-transform: uppercase;
    letter-spacing: 1px;
}
.btn:hover { border-color: var(--accent); transform: translateY(-1px); box-shadow: var(--glow-cyan); }
.btn-primary {
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    color: #fff;
    border: none;
    font-weight: 700;
    box-shadow: var(--glow-cyan);
    clip-path: polygon(8px 0, 100% 0, 100% calc(100% - 8px), calc(100% - 8px) 100%, 0 100%, 0 8px);
}
.btn-primary:hover { box-shadow: 0 0 30px rgba(0, 212, 255, 0.6); }
.btn-block { width: 100%; }

/* ===== Auth ===== */
.auth-container { display: flex; justify-content: center; padding-top: 70px; }
.auth-card {
    background: linear-gradient(160deg, #0d1526, #080d18);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 40px;
    width: 100%;
    max-width: 440px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.6), 0 0 50px rgba(0, 212, 255, 0.1);
    clip-path: polygon(16px 0, 100% 0, 100% calc(100% - 16px), calc(100% - 16px) 100%, 0 100%, 0 16px);
}
.auth-card h1 { font-size: 1.8rem; margin-bottom: 4px; background: linear-gradient(90deg, var(--accent), var(--accent-2)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; text-transform: uppercase; letter-spacing: 2px; }
.auth-sub { color: var(--muted); margin-bottom: 28px; }
.auth-card label { display: block; margin-bottom: 6px; font-size: 0.85rem; color: var(--muted); text-transform: uppercase; letter-spacing: 1px; }
.auth-card input {
    width: 100%;
    background: rgba(3, 5, 10, 0.8);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 13px 16px;
    border-radius: 6px;
    margin-bottom: 20px;
    font-size: 0.95rem;
    font-family: 'Share Tech Mono', monospace;
    transition: border-color 0.2s;
}
.auth-card input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px rgba(0, 212, 255, 0.15), var(--glow-cyan); }
.auth-error {
    background: rgba(255,45,45,0.1);
    color: var(--red);
    padding: 12px 16px;
    border-radius: 6px;
    margin-bottom: 20px;
    font-size: 0.9rem;
    border: 1px solid rgba(255,45,45,0.3);
}
.auth-switch { text-align: center; margin-top: 22px; color: var(--muted); font-size: 0.9rem; }
.auth-switch a { color: var(--accent); text-decoration: none; font-weight: 600; }

/* ===== Classifica ===== */
.leaderboard-wrap { background: var(--card); border: 1px solid var(--border); border-radius: 12px; overflow: hidden; backdrop-filter: blur(8px); }
.leaderboard { width: 100%; border-collapse: collapse; }
.leaderboard th {
    text-align: left;
    padding: 16px 22px;
    background: rgba(5, 7, 13, 0.9);
    color: var(--muted);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    font-family: 'Orbitron', sans-serif;
}
.leaderboard td { padding: 16px 22px; border-top: 1px solid var(--border); }
.leaderboard tr:hover td { background: rgba(0, 212, 255, 0.05); }
.leaderboard .rank { font-weight: 800; color: var(--accent); }
.leaderboard .rank-1 { color: #ffd700; text-shadow: 0 0 10px rgba(255, 215, 0, 0.6); }
.leaderboard .rank-2 { color: #c0c0c0; }
.leaderboard .rank-3 { color: #cd7f32; }
.leaderboard .username { font-weight: 600; }
.leaderboard .points { font-weight: 800; background: linear-gradient(90deg, var(--accent-2), var(--accent-3)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 28px;
    color: var(--muted);
    font-size: 0.85rem;
    border-top: 1px solid var(--border);
    background: rgba(5, 7, 13, 0.6);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.hidden { display: none !important; }
.loading { text-align: center; color: var(--muted); padding: 50px; font-size: 1.1rem; }

/* ===== Scrollbar ===== */
::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 5px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent); }

/* ===== Responsive ===== */
@media (max-width: 640px) {
    .hero h1 { font-size: 2rem; }
    .challenges-grid { grid-template-columns: 1fr; }
    .nav-links { gap: 16px; }
    .hero-stats { gap: 20px; }
}