:root {
    --bg-main: #f8fafc;
    --bg-card: #ffffff;
    --border-soft: #e2e8f0;
    --text-primary: #0f172a;
    --text-second: #64748b;
    --accent: #3b82f6;
    --danger: #ef4444;
    --success: #10b981;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.05), 0 2px 4px -1px rgba(0,0,0,0.03);
    --shadow-lg: 0 10px 25px -3px rgba(0,0,0,0.05);
}

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

body {
    font-family: 'Inter', -apple-system, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
}

.app-layout {
    width: 100%;
    max-width: 1200px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background: var(--bg-card);
    box-shadow: var(--shadow-lg);
}

/* ================================================= HEADERS & TABS */
.top-nav {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 30px 20px 0;
    border-bottom: 1px solid var(--border-soft);
    background: var(--bg-card);
}

.assignment-info {
    text-align: center;
    margin-bottom: 25px;
}

.assignment-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 5px;
    letter-spacing: -0.5px;
}

.assignment-course {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--accent);
    margin-bottom: 4px;
}

.assignment-student {
    font-size: 0.85rem;
    color: var(--text-second);
    font-weight: 500;
}

.tab-controls {
    display: flex;
    gap: 10px;
    background: var(--bg-main);
    padding: 6px;
    border-radius: 12px;
    margin-bottom: -1px; /* overlap border */
}

.tab-btn {
    appearance: none; border: none; background: transparent;
    padding: 10px 24px;
    border-radius: 8px;
    font-weight: 500; font-size: 0.9rem;
    color: var(--text-second);
    cursor: pointer;
    transition: all 0.2s;
}

.tab-btn.active {
    background: var(--bg-card);
    color: var(--text-primary);
    box-shadow: var(--shadow-sm);
}

/* ================================================= MAIN CANVAS */
.canvas-area {
    flex: 1;
    position: relative;
    overflow-y: visible;
    background: var(--bg-main);
    padding: 15px;
    display: flex;
    flex-direction: column;
}

.sim-view {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    flex: 1;
    width: 100%;
    animation: fadeIn 0.3s ease;
}

.sim-view.active {
    display: flex;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.view-title { text-align: center; margin-bottom: 20px; }
.view-title h2 { font-size: 1.2rem; font-weight: 600; margin-bottom: 5px; }
.view-title p { color: var(--text-second); font-size: 0.85rem; }

/* ================================================= TOPOLOGY NODES */
.topology {
    display: flex;
    width: 100%;
    justify-content: center;
    align-items: center;
}

.linear-topology { gap: 40px; }
.tree-topology { flex-direction: column; gap: 20px; }

.node-level { display: flex; justify-content: center; gap: 80px; width: 100%; }

.node-wrapper {
    display: flex; flex-direction: column; align-items: center; gap: 12px;
}

.label { font-size: 0.8rem; font-weight: 500; color: var(--text-second); }

.node {
    background: var(--bg-card);
    border: 1px solid var(--border-soft);
    border-radius: 20px;
    box-shadow: var(--shadow-md);
    display: flex; justify-content: center; align-items: center;
    transition: transform 0.2s, box-shadow 0.2s;
}

.node:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }

.icon { font-size: 1.8rem; text-align: center; line-height: 1.1; display: flex; flex-direction: column; justify-content: center; align-items: center; }

/* Specific Nodes */
.phone-node {
    width: 140px; height: 180px; border-radius: 20px; border: 4px solid #cbd5e1;
    padding: 8px; align-items: flex-start;
}
.ui-screen {
    width: 100%; height: 100%; background: var(--bg-main); border-radius: 10px;
    padding: 10px 5px; display: flex; flex-direction: column; gap: 10px; text-align: center; font-size: 0.75rem; font-weight: 500; justify-content: center;
}
.hub-node { width: 70px; height: 70px; border-radius: 50%; border: 3px solid var(--accent); }
.device-node, .sensor-node { width: 70px; height: 70px; border-radius: 15px;}

.link-label { font-size: 0.75rem; color: var(--text-second); letter-spacing: 1px; text-transform: uppercase; border-bottom: 1px dashed var(--border-soft); padding-bottom: 4px;}

/* Buttons inside views */
.action-btn {
    margin-top: auto; padding: 10px; border: none; background: #e2e8f0; border-radius: 8px; font-weight: 600; cursor: pointer; transition: background 0.2s; width: 100%;
}
.action-btn.danger { background: #fee2e2; color: var(--danger); margin-top: 0; margin-bottom: 15px; }
.action-btn:hover { filter: brightness(0.95); }
.action-btn.active { background: var(--success); color: white; }

/* Status Styles */
.light-icon.on { text-shadow: 0 0 20px #fde047; transform: scale(1.1); transition: 0.2s;}
.hidden-notif { opacity: 0; transform: translateY(10px); transition: 0.2s; background: var(--danger); color: white; padding: 10px; border-radius: 8px; }
.hidden-notif.show { opacity: 1; transform: translateY(0); }
.pop-notif { position: absolute; top: -25px; font-size: 0.7rem; z-index: 10; white-space: nowrap; box-shadow: var(--shadow-md); }
.active-pulse { animation: pulseBorder 1s infinite alternate; }
@keyframes pulseBorder { from { border-color: var(--border-soft); box-shadow: 0 0 0; } to { border-color: var(--accent); box-shadow: 0 0 15px rgba(59,130,246,0.3); } }

/* ================================================= FOOTER ANALYTICS */
.analytics-panel {
    display: flex;
    background: var(--bg-card);
    border-top: 1px solid var(--border-soft);
    height: 180px;
    flex-shrink: 0;
}

.panel-section {
    padding: 15px 25px;
    border-right: 1px solid var(--border-soft);
}

.panel-lbl { font-size: 0.75rem; font-weight: 600; color: var(--text-second); text-transform: uppercase; margin-bottom: 15px; display: block; }

.control-box { flex: 1; display:flex; flex-direction:column; justify-content:center; }
input[type=range] { width: 100%; margin-bottom: 10px; accent-color: var(--accent); }
.val { font-size: 0.9rem; font-weight: 500; }

.stats-box { flex: 1; display: flex; gap: 30px; align-items: center; }
.stat-item { display: flex; flex-direction: column; gap: 5px; }
.stat-lbl { font-size: 0.8rem; color: var(--text-second); }
.stat-val { font-size: 1.8rem; font-weight: 600; letter-spacing: -1px; }
.status-indicator { font-size: 1rem; color: var(--accent); font-weight: 500; letter-spacing: 0; }

.log-box { flex: 2; display: flex; flex-direction: column; border-right: none; overflow: hidden; }
.feed-container {
    flex: 1; background: var(--bg-main); border-radius: 8px; padding: 12px;
    font-family: ui-monospace, monospace; font-size: 0.75rem;
    overflow-y: auto; display: flex; flex-direction: column; gap: 6px;
    border: 1px solid var(--border-soft); box-shadow: inset var(--shadow-sm);
}

.log-row { padding: 4px 0; border-bottom: 1px dashed var(--border-soft); }
.log-row:last-child { border-bottom: none; }
.log-row.info { color: var(--text-second); }
.log-row.event { color: var(--text-primary); }

/* ================================================= PACKET LAYER */
#packetLayer { position: absolute; top:0; left:0; width:100%; height:100%; pointer-events:none; z-index: 100; overflow: visible; }
.packet {
    position: absolute; width: 10px; height: 10px; border-radius: 50%;
    transform: translate(-50%, -50%);
}
.packet.req { background: var(--accent); box-shadow: 0 0 8px var(--accent); }
.packet.res { background: var(--success); box-shadow: 0 0 8px var(--success); }
.packet.pub { background: var(--text-primary); box-shadow: 0 0 8px var(--text-primary); }
.packet.sub { background: var(--danger); box-shadow: 0 0 8px var(--danger); }

/* ================================================= DASHBOARD SCOREBOARD */
.stat-comparison {
    display: flex;
    gap: 20px;
    background: rgba(var(--accent), 0.05);
    padding: 8px 16px;
    border-radius: 8px;
    border: 1px dashed var(--border-soft);
}
.comp-item {
    display: flex;
    flex-direction: column;
    gap: 4px;
}
.comp-divider {
    width: 1px;
    background: var(--border-soft);
    margin: 0 5px;
}
.req-color { color: var(--accent); font-weight: 700; }
.pub-color { color: var(--danger); font-weight: 700; }
.hover-tip { border-bottom: 1px dotted var(--text-second); cursor: help; }

/* ================================================= GLASSMORPHISM EXPLANATION */
.glass-explanation {
    margin: 40px auto 20px auto;
    padding: 24px;
    background: rgba(255, 255, 255, 0.4);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.6);
    border-radius: 16px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.05);
    text-align: left;
    max-width: 800px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.glass-explanation:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.08);
}
.glass-explanation h3 {
    margin: 0 0 20px 0;
    font-size: 1.2rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
    border-bottom: 2px solid rgba(0, 0, 0, 0.05);
    padding-bottom: 12px;
}
.explanation-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}
.explanation-item h4 {
    margin: 0 0 8px 0;
    font-size: 0.95rem;
    color: var(--text-primary);
}
.explanation-item p {
    margin: 0;
    font-size: 0.9rem;
    line-height: 1.6;
    color: var(--text-second);
}