@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
    --bg-color: #0b0f19;
    --card-bg: #151b2b;
    --text-primary: #e2e8f0;
    --text-secondary: #94a3b8;
    --accent-primary: #3b82f6;
    --accent-glow: rgba(59, 130, 246, 0.5);
    --border-color: #1e293b;
    --success: #10b981;
    --nav-height: 70px;
    --font-main: 'Inter', sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-main);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}
::-webkit-scrollbar-track {
    background: var(--bg-color);
}
::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--accent-primary);
}

/* Header & Nav */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: var(--nav-height);
    background: rgba(11, 15, 25, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    display: flex;
    align-items: center;
    padding: 0 2rem;
    justify-content: space-between;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, #fff 0%, var(--accent-primary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-item {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.2s ease;
    padding: 0.5rem 0.75rem;
    border-radius: 6px;
}

.nav-item:hover, .nav-item.active {
    color: #fff;
    background: rgba(255, 255, 255, 0.05);
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: #fff;
    font-size: 1.5rem;
    cursor: pointer;
}

/* Main Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: calc(var(--nav-height) + 2rem) 2rem 4rem;
    display: flex;
    gap: 3rem;
}

.sidebar {
    width: 250px;
    flex-shrink: 0;
    position: sticky;
    top: calc(var(--nav-height) + 2rem);
    height: calc(100vh - var(--nav-height) - 4rem);
    overflow-y: auto;
    padding-right: 1rem;
    display: none; /* Hidden on small screens initially, or we can make it TOC */
}

/* We will stick to a simpler top-down flow for mobile friendliness as primary request */
/* Actually, let's keep the nav fixed on top and just have specific weeks in sections */

/* Sections */
section {
    margin-bottom: 4rem;
    scroll-margin-top: calc(var(--nav-height) + 2rem);
    opacity: 0;
    transform: translateY(20px);
    animation: fadeIn 0.6s ease forwards;
}

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

.week-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
}
.week-title::after {
    content: '';
    height: 1px;
    flex-grow: 1;
    background: linear-gradient(90deg, var(--border-color), transparent);
}

/* Challenge Cards */
.challenge-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    margin-bottom: 2rem;
    overflow: hidden;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    transition: transform 0.2s;
}

.challenge-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.challenge-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: #fff;
}

/* Tabs */
.code-tabs {
    display: flex;
    background: rgba(0,0,0,0.2);
    padding: 0 1rem;
    border-bottom: 1px solid var(--border-color);
}

.tab-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    padding: 1rem 1.5rem;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: all 0.2s;
}

.tab-btn:hover {
    color: #fff;
}

.tab-btn.active {
    color: var(--accent-primary);
    border-bottom-color: var(--accent-primary);
}

/* Code Block */
.code-container {
    position: relative;
    background: #0d1117; /* Matches typical Prism Dark themes */
}

.code-panel {
    display: none;
    padding: 1rem;
    overflow-x: auto;
}

.code-panel.active {
    display: block;
}

pre {
    margin: 0 !important;
    background: transparent !important;
    border-radius: 0 !important;
    font-family: var(--font-mono) !important;
}

/* Copy Button */
.copy-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s;
    backdrop-filter: blur(4px);
    z-index: 10;
}

.copy-btn:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateY(-1px);
}

.copy-btn.copied {
    background: var(--success);
    border-color: var(--success);
    color: #fff;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        top: var(--nav-height);
        left: 0;
        width: 100%;
        background: var(--card-bg);
        flex-direction: column;
        padding: 2rem;
        gap: 1.5rem;
        border-bottom: 1px solid var(--border-color);
        transform: translateY(-100%);
        opacity: 0;
        transition: all 0.3s ease-in-out;
        z-index: 999;
        pointer-events: none;
    }

    .nav-links.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: all;
    }

    .menu-toggle {
        display: block;
    }
    
    .container {
        padding: calc(var(--nav-height) + 1rem) 1rem 2rem;
    }
    
    .code-tabs {
        overflow-x: auto;
    }
}