:root {
    --bg-main: #0b0f17;
    --bg-card: #141c2e;
    --bg-card-hover: #1c273e;
    --bg-sidebar: #0f1623;
    --bg-terminal: #070a10;
    --border-color: #23314d;
    --border-highlight: #38bdf8;
    
    --text-main: #f1f5f9;
    --text-muted: #94a3b8;
    --text-dim: #64748b;
    
    --accent-blue: #38bdf8;
    --accent-green: #10b981;
    --accent-purple: #8b5cf6;
    --accent-amber: #f59e0b;
    --accent-red: #ef4444;
    
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'Fira Code', Consolas, Monaco, monospace;

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.4);
    --shadow-glow: 0 0 15px rgba(56, 189, 248, 0.25);
}

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

body {
    background-color: var(--bg-main);
    color: var(--text-main);
    font-family: var(--font-sans);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header Styling */
.app-header {
    background: linear-gradient(180deg, #111827 0%, var(--bg-sidebar) 100%);
    border-bottom: 1px solid var(--border-color);
    padding: 16px 24px;
}

.header-container {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.brand {
    display: flex;
    align-items: center;
    gap: 14px;
}

.logo-icon {
    width: 44px;
    height: 44px;
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    box-shadow: var(--shadow-glow);
}

.brand h1 {
    font-size: 1.35rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: #fff;
}

.subtitle {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.student-badge {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    padding: 8px 16px;
    border-radius: 30px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.badge-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.badge-status {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent-amber);
}

/* Main Layout */
.main-layout {
    display: flex;
    flex: 1;
    max-width: 1400px;
    width: 100%;
    margin: 0 auto;
}

/* Sidebar Navigation */
.sidebar {
    width: 320px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    padding: 24px 16px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.student-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
}

.student-card h3 {
    font-size: 0.95rem;
    margin-bottom: 12px;
    color: var(--accent-blue);
    display: flex;
    align-items: center;
    gap: 8px;
}

.form-group {
    margin-bottom: 10px;
}

.form-group label {
    display: block;
    font-size: 0.78rem;
    color: var(--text-muted);
    margin-bottom: 4px;
}

.form-group input {
    width: 100%;
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    color: var(--text-main);
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.88rem;
    transition: border-color 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--accent-blue);
}

.module-nav {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.nav-title {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-dim);
    margin-left: 8px;
    margin-bottom: 4px;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 12px;
    width: 100%;
    padding: 12px 14px;
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    color: var(--text-muted);
    font-family: var(--font-sans);
    font-size: 0.88rem;
    text-align: left;
    cursor: pointer;
    transition: all 0.2s ease;
}

.nav-btn:hover {
    background: var(--bg-card-hover);
    color: var(--text-main);
}

.nav-btn.active {
    background: var(--bg-card);
    border-color: var(--accent-blue);
    color: var(--accent-blue);
    font-weight: 600;
    box-shadow: var(--shadow-glow);
}

.step-num {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.08);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 700;
}

.nav-btn.active .step-num {
    background: var(--accent-blue);
    color: var(--bg-main);
}

.step-label {
    flex: 1;
}

.status-icon {
    font-size: 0.9rem;
    color: var(--text-dim);
}

.status-icon.done {
    color: var(--accent-green);
    font-weight: bold;
}

/* Sidebar Footer & Progress */
.sidebar-footer {
    margin-top: auto;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

.progress-info {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 6px;
}

.progress-track {
    width: 100%;
    height: 8px;
    background: var(--bg-terminal);
    border-radius: 4px;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-blue), var(--accent-green));
    transition: width 0.4s ease;
}

/* Main Content Area */
.content-area {
    flex: 1;
    padding: 32px 40px;
    overflow-y: auto;
}

.tab-module {
    display: none;
    animation: fadeIn 0.3s ease;
}

.tab-module.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

.module-header {
    margin-bottom: 28px;
}

.module-tag {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--accent-blue);
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.module-header h2 {
    font-size: 1.8rem;
    font-weight: 700;
    color: #fff;
    margin: 4px 0 8px 0;
}

.module-header p {
    color: var(--text-muted);
    font-size: 1.02rem;
}

/* Cards & Layout Grid */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-md);
}

.highlight-card {
    border-color: var(--border-highlight);
    box-shadow: var(--shadow-glow);
}

.margin-top {
    margin-top: 24px;
}

.grid-2col {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

@media (max-width: 1024px) {
    .main-layout { flex-direction: column; }
    .sidebar { width: 100%; }
    .grid-2col { grid-template-columns: 1fr; }
}

.card h3 {
    font-size: 1.15rem;
    font-weight: 600;
    color: #fff;
    margin-bottom: 14px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.bullet-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.bullet-list li {
    position: relative;
    padding-left: 20px;
    color: var(--text-muted);
    font-size: 0.95rem;
}

.bullet-list li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--accent-blue);
    font-size: 1.3rem;
    line-height: 1;
}

/* Topology Diagram */
.topology-diagram {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px;
    text-align: center;
}

.topo-node {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 12px;
    display: inline-block;
    min-width: 180px;
}

.topo-node.pihole { border-color: var(--accent-green); }
.topo-node.winclient { border-color: var(--accent-blue); }

.node-icon { font-size: 1.5rem; }
.node-title { font-weight: 600; font-size: 0.88rem; color: #fff; }
.node-sub { font-size: 0.75rem; color: var(--text-dim); }

.topo-connect {
    margin: 12px 0;
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--accent-purple);
}

.topo-children {
    display: flex;
    justify-content: center;
    gap: 20px;
}

/* Terminal Styling */
.terminal-box {
    background-color: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.terminal-header {
    background: rgba(255, 255, 255, 0.04);
    border-bottom: 1px solid var(--border-color);
    padding: 8px 14px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-muted);
}

.terminal-box pre {
    padding: 16px;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: #e2e8f0;
    overflow-x: auto;
    line-height: 1.5;
}

.prompt { color: var(--accent-green); font-weight: 600; }
.comment { color: var(--text-dim); font-style: italic; }
.output { color: var(--text-muted); }

.btn-copy {
    background: rgba(56, 189, 248, 0.1);
    border: 1px solid var(--accent-blue);
    color: var(--accent-blue);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-family: var(--font-sans);
    cursor: pointer;
    transition: all 0.2s;
}

.btn-copy:hover {
    background: var(--accent-blue);
    color: var(--bg-main);
}

/* Interactive Demo / Simulated Browsers */
.interactive-demo-box {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    margin-top: 16px;
}

.demo-toolbar {
    background: #1e293b;
    padding: 10px 14px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.browser-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
}
.browser-dot.red { background: #ef4444; }
.browser-dot.yellow { background: #f59e0b; }
.browser-dot.green { background: #10b981; }

.url-bar {
    flex: 1;
    background: #0f172a;
    border-radius: var(--radius-sm);
    padding: 4px 12px;
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-muted);
    margin: 0 12px;
}

.status-tag {
    font-size: 0.75rem;
    padding: 4px 10px;
    border-radius: 20px;
    font-weight: 600;
}

.tag-unfiltered { background: rgba(239, 68, 68, 0.2); color: var(--accent-red); border: 1px solid var(--accent-red); }
.tag-pihole { background: rgba(16, 185, 129, 0.2); color: var(--accent-green); border: 1px solid var(--accent-green); }
.tag-opendns { background: rgba(139, 92, 246, 0.2); color: var(--accent-purple); border: 1px solid var(--accent-purple); }

.mock-browser-body {
    background: #ffffff;
    color: #1e293b;
    padding: 24px;
    min-height: 220px;
}

.news-header h2 { font-size: 1.4rem; color: #0f172a; }
.pub-date { font-size: 0.8rem; color: #64748b; }

.ad-banner-box {
    margin: 16px 0;
    padding: 16px;
    border-radius: var(--radius-md);
    border: 2px dashed #cbd5e1;
}

.intrusive-ad {
    background: #fff1f2;
    border-color: #f43f5e;
    color: #9f1239;
}

.gambling-ad {
    background: #fffbeb;
    border-color: #f59e0b;
    color: #92400e;
}

.ad-label {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    display: block;
    margin-bottom: 4px;
}

.ad-btn {
    margin-top: 10px;
    background: #e11d48;
    color: #fff;
    border: none;
    padding: 6px 14px;
    border-radius: 4px;
    font-weight: 600;
    cursor: pointer;
}

.blocked-ad {
    background: #f0fdf4;
    border-color: #22c55e;
    text-align: center;
    padding: 20px;
}

.blocked-badge {
    color: #15803d;
    font-weight: 700;
    font-size: 0.9rem;
}

.blocked-sub {
    font-size: 0.8rem;
    color: #166534;
}

/* OpenDNS Block Page Simulation */
.opendns-block-page {
    background: #0f172a;
    color: #f8fafc;
    padding: 30px;
    border-radius: var(--radius-md);
    text-align: center;
}

.opendns-logo { font-size: 1.2rem; font-weight: 700; color: var(--accent-purple); margin-bottom: 10px; }
.block-heading { font-size: 1.3rem; color: #ef4444; margin-bottom: 10px; }
.block-msg { color: #cbd5e1; font-size: 0.95rem; margin-bottom: 16px; }
.block-details { font-size: 0.8rem; color: #94a3b8; font-family: var(--font-mono); }

/* Proxmox Spec Grid */
.spec-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 14px;
    margin-top: 14px;
}

.spec-card {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    padding: 12px 14px;
    border-radius: var(--radius-md);

}

.spec-title { font-size: 0.75rem; color: var(--text-dim); display: block; }
.spec-val { font-size: 0.95rem; font-weight: 600; color: var(--accent-blue); }

.step-instructions {
    margin-left: 20px;
    color: var(--text-muted);
    font-size: 0.92rem;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.wizard-walkthrough {
    margin-top: 16px;
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border-color);
    padding: 16px;
    border-radius: var(--radius-md);
}

.wizard-walkthrough h4 { margin-bottom: 10px; color: #fff; }

/* Checklist Item */
.checklist-item {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    padding: 16px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: 14px;
}

.task-check {
    width: 20px;
    height: 20px;
    accent-color: var(--accent-green);
    cursor: pointer;
}

.checklist-item label {
    font-size: 0.92rem;
    color: var(--text-muted);
    cursor: pointer;
}

/* Sub-tabs */
.tab-group { margin-top: 14px; }
.tab-buttons { display: flex; gap: 8px; margin-bottom: 12px; }

.tab-btn {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    color: var(--text-muted);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.85rem;
}

.tab-btn.active {
    background: var(--accent-blue);
    color: var(--bg-main);
    border-color: var(--accent-blue);
    font-weight: 600;
}

.subtab-content { display: none; }
.subtab-content.active { display: block; }

/* DNS Pair Grid */
.dns-pair-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-top: 14px;
}

.pair-card {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
}

.pair-card.highlight-border {
    border-color: var(--accent-purple);
}

.pair-card h4 { color: #fff; margin-bottom: 8px; font-size: 0.95rem; }
.pair-card p { font-size: 0.88rem; color: var(--text-muted); }

/* Simulator Controls */
.simulator-controls {
    display: flex;
    flex-direction: column;
    gap: 14px;
    margin-top: 16px;
}

.mode-selector {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.mode-selector label { font-size: 0.85rem; color: var(--text-muted); }

.mode-selector select {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    color: var(--accent-blue);
    padding: 10px;
    border-radius: var(--radius-sm);
    font-size: 0.92rem;
    font-family: var(--font-sans);
}

.query-input-group {
    display: flex;
    gap: 10px;
}

.query-input-group input {
    flex: 1;
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    color: #fff;
    padding: 10px 14px;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
}

.preset-buttons {
    display: flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    margin-top: 14px;
}

.preset-buttons span { font-size: 0.8rem; color: var(--text-dim); }

.chip-btn {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    color: var(--text-muted);
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.78rem;
    font-family: var(--font-mono);
    cursor: pointer;
    transition: all 0.2s;
}

.chip-btn:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
}

/* Simulator Visual Stage */
.sim-visual-stage {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 24px;
    margin-top: 20px;
    display: flex;
    justify-content: space-around;
    align-items: center;
}

.sim-node {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    padding: 12px 18px;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.3s ease;
}

.sim-node.active-pass { border-color: var(--accent-green); box-shadow: 0 0 15px rgba(16, 185, 129, 0.4); }
.sim-node.active-block { border-color: var(--accent-red); box-shadow: 0 0 15px rgba(239, 68, 68, 0.4); }

.sim-arrow { font-size: 1.4rem; color: var(--text-dim); }

.sim-output-box {
    margin-top: 16px;
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.output-header {
    background: rgba(255, 255, 255, 0.04);
    padding: 8px 14px;
    font-size: 0.8rem;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border-color);
}

.output-content {
    padding: 16px;
    font-family: var(--font-mono);
    font-size: 0.88rem;
    color: #e2e8f0;
    white-space: pre-wrap;
    min-height: 120px;
}

/* Quiz Styling */
.quiz-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
    margin-top: 16px;
}

.quiz-item {
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 18px;
}

.quiz-question { font-weight: 600; font-size: 0.95rem; margin-bottom: 12px; color: #fff; }

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.quiz-options label {
    font-size: 0.88rem;
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 10px;
}

.quiz-result-box {
    margin-top: 14px;
    padding: 14px;
    border-radius: var(--radius-md);
    font-weight: 600;
}

.quiz-result-box.pass { background: rgba(16, 185, 129, 0.15); border: 1px solid var(--accent-green); color: var(--accent-green); }
.quiz-result-box.fail { background: rgba(239, 68, 68, 0.15); border: 1px solid var(--accent-red); color: var(--accent-red); }

/* Reflection Textarea */
#reflectionNotes {
    width: 100%;
    margin-top: 12px;
    background: var(--bg-terminal);
    border: 1px solid var(--border-color);
    color: #fff;
    padding: 12px;
    border-radius: var(--radius-md);
    font-family: var(--font-sans);
    font-size: 0.9rem;
}

/* Buttons & Footer Nav */
.btn {
    padding: 10px 20px;
    border-radius: var(--radius-md);
    border: none;
    font-weight: 600;
    font-size: 0.9rem;
    font-family: var(--font-sans);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: all 0.2s ease;
}

.btn-primary { background: var(--accent-blue); color: var(--bg-main); }
.btn-primary:hover { background: #0284c7; box-shadow: var(--shadow-glow); }

.btn-secondary { background: var(--bg-terminal); border: 1px solid var(--border-color); color: var(--text-main); }
.btn-secondary:hover { background: var(--bg-card-hover); }

.btn-success { background: var(--accent-green); color: #042f2e; }
.btn-success:hover { background: #059669; }

.btn-lg { padding: 14px 28px; font-size: 1.05rem; }

.module-footer {
    display: flex;
    justify-content: space-between;
    margin-top: 32px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.align-center { text-align: center; }
.export-actions { margin-top: 16px; }

/* Modal & Printable Report */
.modal {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal.hidden { display: none; }

.modal-content {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.modal-header {
    padding: 16px 24px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-body {
    padding: 24px;
    overflow-y: auto;
    color: var(--text-main);
}

.modal-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

.close-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
}

.callout-info {
    background: rgba(56, 189, 248, 0.1);
    border-left: 4px solid var(--accent-blue);
    padding: 12px 16px;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    font-size: 0.9rem;
}

.hidden { display: none !important; }