:root {
    --bg-primary: #020617;
    --bg-secondary: rgba(15, 23, 42, 0.8);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent: #38bdf8;
    --accent-gradient: linear-gradient(135deg, #38bdf8 0%, #818cf8 100%);
    --card-bg: rgba(30, 41, 59, 0.5);
    --border: rgba(255, 255, 255, 0.08);
    --sidebar-width: 320px;
    --shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-primary);
    background-image:
        radial-gradient(circle at 0% 0%, rgba(56, 189, 248, 0.05) 0%, transparent 50%),
        radial-gradient(circle at 100% 100%, rgba(129, 140, 248, 0.05) 0%, transparent 50%);
    color: var(--text-primary);
    line-height: 1.6;
    display: flex;
    height: 100vh;
    overflow: hidden;
}

/* Sidebar Overhaul */
aside {
    width: var(--sidebar-width);
    background-color: var(--bg-secondary);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    z-index: 10;
}

.back-btn {
    margin: 1.5rem 1.5rem 0.5rem 1.5rem;
    padding: 0.75rem 1rem;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border);
    border-radius: 12px;
    color: var(--accent);
    font-size: 0.9rem;
    font-weight: 700;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s;
    justify-content: center;
}

.back-btn:hover {
    background: var(--accent);
    color: #000;
    transform: scale(1.02);
}

.sidebar-nav {
    padding: 1rem 0 3rem 0;
}

.nav-section {
    padding: 1.5rem 2rem 0.5rem 2rem;
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    opacity: 0.8;
}

.nav-item {
    margin: 0.25rem 1rem;
    padding: 0.875rem 1rem;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 0.9rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    border: 1px solid transparent;
}

.nav-item:hover {
    background-color: rgba(255, 255, 255, 0.03);
    color: var(--text-primary);
    transform: translateX(4px);
}

.nav-item.active {
    background-color: rgba(56, 189, 248, 0.1);
    color: var(--text-primary);
    border: 1px solid rgba(56, 189, 248, 0.2);
    font-weight: 600;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* Main Content */
main {
    flex: 1;
    overflow-y: auto;
    padding: 4rem;
    display: flex;
    justify-content: center;
}

#lesson-container {
    max-width: 800px;
    width: 100%;
    animation: fadeIn 0.5s ease-out;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.content-header h2 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 2rem;
    letter-spacing: -0.04em;
}

.lesson-body {
    font-size: 1.15rem;
    color: var(--text-secondary);
}

.lesson-body p {
    margin-bottom: 1.75rem;
}

.lesson-body h3 {
    color: var(--text-primary);
    margin: 3rem 0 1.25rem;
    font-size: 1.5rem;
    font-weight: 700;
}

.lesson-body blockquote {
    background: var(--card-bg);
    border-left: 4px solid var(--accent);
    padding: 2rem;
    margin: 2.5rem 0;
    border-radius: 12px;
    font-style: italic;
    box-shadow: var(--shadow);
}

/* Code Blocks */
.code-container {
    position: relative;
    margin: 3rem 0;
    background-color: #0f172a;
    border-radius: 12px;
    border: 1px solid var(--border);
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.3);
    overflow: hidden;
}

.code-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1.25rem;
    background-color: rgba(255, 255, 255, 0.03);
    border-bottom: 1px solid var(--border);
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.copy-btn {
    background: rgba(56, 189, 248, 0.1);
    border: 1px solid rgba(56, 189, 248, 0.2);
    color: var(--accent);
    padding: 0.4rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.75rem;
    font-weight: 600;
    transition: all 0.2s;
}

.copy-btn:hover {
    background-color: var(--accent);
    color: #000;
}

pre {
    padding: 2rem;
    overflow-x: auto;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* Sidebar Toggling */
body.is-landing {
    overflow-y: auto;
    height: auto;
    min-height: 100vh;
}

body.is-landing .back-btn {
    display: none;
}

body.is-landing aside {
    display: none;
}

body.is-landing main {
    padding: 0;
    max-width: 100%;
    overflow: visible;
}

/* Mascot Styles */
.hero-mascot {
    width: 280px;
    height: auto;
    margin-bottom: 3rem;
    filter: drop-shadow(0 0 40px rgba(56, 189, 248, 0.2));
    animation: float 4s ease-in-out infinite;
}

@keyframes float {

    0%,
    100% {
        transform: translateY(0) rotate(0deg);
    }

    50% {
        transform: translateY(-30px) rotate(2deg);
    }
}

/* Landing Page Styles */
.landing-view {
    max-width: 1400px;
    width: 100%;
    margin: 0 auto;
    padding: 6rem 2rem 10rem 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    /* justify-content: center removed to prevent clipping */
    min-height: 100vh;
    animation: fadeIn 1s cubic-bezier(0.4, 0, 0.2, 1);
}

.hero {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 5rem;
    width: 100%;
    text-align: left;
    padding-bottom: 8rem;
}

.hero-content {
    flex: 1;
}

.hero-mascot-container {
    flex: 0 0 auto;
    display: flex;
    justify-content: center;
    order: -1;
    /* Mascot on the left */
}

.hero h1 {
    font-size: 5rem;
    font-weight: 950;
    line-height: 1.05;
    margin-bottom: 2rem;
    letter-spacing: -0.06em;
    background: linear-gradient(135deg, #fff 30%, #94a3b8 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero p {
    font-size: 1.65rem;
    color: var(--text-secondary);
    max-width: 650px;
    margin: 0 0 4rem 0;
    line-height: 1.6;
    font-weight: 400;
}

.hero-btn {
    background: var(--accent-gradient);
    color: #000;
    padding: 1.6rem 4.5rem;
    border-radius: 100px;
    font-weight: 800;
    font-size: 1.4rem;
    cursor: pointer;
    border: none;
    transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    box-shadow: 0 20px 50px rgba(56, 189, 248, 0.3);
}

.hero-btn:hover {
    transform: translateY(-8px) scale(1.05);
    box-shadow: 0 40px 80px rgba(56, 189, 248, 0.4);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 4rem;
    margin-top: 2rem;
    max-width: 1200px;
    width: 100%;
}

.feature-card {
    background: rgba(30, 41, 59, 0.4);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 4rem;
    border-radius: 40px;
    border: 1px solid rgba(255, 255, 255, 0.08);
    transition: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
    position: relative;
}

.feature-card:hover {
    border-color: rgba(56, 189, 248, 0.4);
    background: rgba(30, 41, 59, 0.7);
    transform: translateY(-15px);
    box-shadow: 0 50px 100px -20px rgba(0, 0, 0, 0.6);
}

.feature-card h3 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--accent);
    letter-spacing: -0.02em;
    font-weight: 800;
}

.feature-card p {
    font-size: 1.2rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* Sidebar Home Link Refinement */
.home-link {
    margin: 2.5rem 1.5rem 1rem 1.5rem;
    padding: 1.4rem;
    background: rgba(56, 189, 248, 0.08);
    border: 1px solid rgba(56, 189, 248, 0.15);
    border-radius: 20px;
    cursor: pointer;
    color: var(--accent);
    font-weight: 800;
    text-align: center;
    transition: all 0.3s;
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.home-link:hover {
    background: var(--accent);
    color: #000;
    transform: scale(1.05);
}

/* Responsive (Final Polish) */
@media (max-width: 1024px) {
    .hero {
        flex-direction: column;
        text-align: center;
        gap: 2rem;
    }

    .hero p {
        margin: 0 auto 3rem auto;
    }

    .features-grid {
        grid-template-columns: 1fr;
        gap: 2.5rem;
    }

    .hero h1 {
        font-size: 4rem;
    }

    .hero p {
        font-size: 1.4rem;
    }

    .landing-view {
        padding: 6rem 1.5rem;
    }

    .feature-card {
        padding: 3rem;
    }

    .hero-mascot {
        width: 220px;
    }
}