:root {
    --bg-color: #0b0f19;
    --panel-bg: rgba(22, 27, 34, 0.75);
    --border-color: rgba(255, 255, 255, 0.1);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-color: #f74c00; /* Rust orange */
    --accent-hover: #ff6a22;
    --glass-blur: blur(12px);
    --radius-lg: 16px;
    --radius: 10px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Plus Jakarta Sans', sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Splash Screen */
#splash-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: var(--bg-color);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    transition: opacity 0.5s;
}

.loader {
    text-align: center;
}

.loader img {
    width: 80px;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% { transform: scale(0.95); opacity: 0.8; }
    50% { transform: scale(1.05); opacity: 1; }
    100% { transform: scale(0.95); opacity: 0.8; }
}

/* Glassmorphism */
.glass-panel {
    background: var(--panel-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
}

/* Cross-Module Top Navigation Bar */
.cross-nav-bar {
    background: rgba(11, 15, 25, 0.95);
    border-bottom: 1px solid var(--border-color);
    padding: 6px 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 0.85rem;
    overflow-x: auto;
    white-space: nowrap;
    z-index: 101;
}

.cross-nav-links {
    display: flex;
    align-items: center;
    gap: 12px;
}

.cross-nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 4px 10px;
    border-radius: 6px;
    font-weight: 500;
    transition: var(--transition);
}

.cross-nav-links a:hover,
.cross-nav-links a.active {
    background: rgba(247, 76, 0, 0.15);
    color: var(--accent-color);
    font-weight: 700;
}

.cross-nav-links a.quiz-pill {
    background: linear-gradient(135deg, rgba(234, 179, 8, 0.2), rgba(247, 76, 0, 0.2));
    color: #eab308;
    border: 1px solid rgba(234, 179, 8, 0.4);
    font-weight: 700;
}

/* Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 2rem;
    background: var(--panel-bg);
    backdrop-filter: var(--glass-blur);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 800;
    font-size: 1.25rem;
    color: var(--text-primary);
    text-decoration: none;
}

.logo img {
    height: 32px;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.search-box {
    position: relative;
}

.search-box i {
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.search-box input {
    background: rgba(0, 0, 0, 0.25);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.45rem 1rem 0.45rem 2.2rem;
    border-radius: 20px;
    outline: none;
    font-size: 0.85rem;
    width: 220px;
    transition: var(--transition);
}

.search-box input:focus {
    border-color: var(--accent-color);
    width: 260px;
}

button {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
}

#theme-btn {
    font-size: 1.1rem;
    padding: 8px;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-selector {
    position: relative;
}

.theme-dropdown {
    display: none;
    position: absolute;
    right: 0;
    top: 45px;
    background: #161b22;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 10px;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    z-index: 1000;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
}

.theme-dropdown.show {
    display: grid;
}

.theme-option {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    cursor: pointer;
    border: 2px solid transparent;
    transition: transform 0.2s;
}

.theme-option:hover {
    transform: scale(1.2);
    border-color: #ffffff;
}

.user-stats {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.xp-badge, .rank-badge {
    background: rgba(0, 0, 0, 0.3);
    padding: 0.35rem 0.8rem;
    border-radius: 12px;
    font-size: 0.85rem;
    font-weight: 700;
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 6px;
}

.xp-badge {
    color: #eab308;
}

.rank-badge {
    color: var(--accent-color);
}

/* Category Filter Bar */
.category-bar {
    display: flex;
    gap: 6px;
    overflow-x: auto;
    padding: 8px 0 12px;
    margin-bottom: 8px;
    border-bottom: 1px solid var(--border-color);
}

.cat-pill {
    padding: 4px 10px;
    border-radius: 6px;
    font-size: 0.78rem;
    font-weight: 600;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    white-space: nowrap;
    cursor: pointer;
    transition: var(--transition);
}

.cat-pill:hover,
.cat-pill.active {
    background: var(--accent-color);
    color: #ffffff;
    border-color: var(--accent-color);
}

/* Layout */
.container {
    display: flex;
    flex: 1;
    overflow: hidden;
}

.sidebar {
    width: 320px;
    background: var(--panel-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 1.25rem;
    overflow-y: auto;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.sidebar-header h3 {
    color: var(--accent-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.1rem;
}

.progress-container {
    height: 6px;
    background: rgba(0, 0, 0, 0.3);
    border-radius: 4px;
    margin-bottom: 0.4rem;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: var(--accent-color);
    width: 0%;
    transition: width 0.3s;
}

.progress-text {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    text-align: right;
}

.topic-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.topic-item {
    padding: 0.65rem 0.85rem;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid transparent;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.topic-item:hover {
    background: rgba(255, 255, 255, 0.05);
}

.topic-item.active {
    background: rgba(247, 76, 0, 0.15);
    border-color: rgba(247, 76, 0, 0.4);
    color: var(--accent-color);
}

.topic-item.completed {
    color: #10b981;
}

/* Content Area */
.content-area {
    flex: 1;
    padding: 1.75rem;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.hero {
    text-align: center;
    padding: 1.75rem 1.5rem;
    background: linear-gradient(135deg, rgba(247, 76, 0, 0.12), rgba(0, 188, 212, 0.05));
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.hero h1 {
    font-size: 2.2rem;
    margin-bottom: 0.35rem;
    color: var(--accent-color);
    font-weight: 800;
}

.hero p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.content-display {
    padding: 1.75rem;
    min-height: 250px;
}

.topic-content h2 {
    color: var(--accent-color);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
}

.topic-content p {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 1.25rem;
    font-size: 0.95rem;
}

.deep-dive, .under-hood, .pro-tip {
    background: rgba(0, 0, 0, 0.25);
    border-radius: var(--radius);
    padding: 1.2rem;
    margin-bottom: 1rem;
    border-left: 4px solid var(--accent-color);
}

.deep-dive h3, .under-hood h3, .pro-tip h3 {
    margin: 0 0 0.5rem 0;
    color: var(--text-primary);
    font-size: 1rem;
    display: flex;
    align-items: center;
    gap: 8px;
}

.deep-dive p, .under-hood p, .pro-tip p {
    margin: 0;
    font-size: 0.9rem;
}

.pro-tip {
    border-left-color: #eab308;
}

.under-hood {
    border-left-color: #38bdf8;
}

/* Playground */
.playground {
    display: flex;
    flex-direction: column;
    min-height: 440px;
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.playground-header {
    padding: 0.85rem 1.25rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(0, 0, 0, 0.3);
    flex-wrap: wrap;
    gap: 10px;
}

.playground-header h3 {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1rem;
}

.playground-actions {
    display: flex;
    align-items: center;
    gap: 8px;
}

.playground-actions select {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 0.85rem;
    outline: none;
    cursor: pointer;
}

.playground-actions button {
    background: var(--accent-color);
    color: #fff;
    padding: 6px 14px;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.85rem;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 6px;
}

.playground-actions button:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

.playground-actions button.secondary {
    background: rgba(255, 255, 255, 0.08);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.editor-container {
    height: 220px;
    display: flex;
}

#code-editor {
    width: 100%;
    height: 100%;
    background: #141821;
    color: #e2e8f0;
    border: none;
    padding: 1rem;
    font-family: 'Consolas', 'Courier New', monospace;
    font-size: 0.95rem;
    line-height: 1.5;
    resize: none;
    outline: none;
}

.output-container {
    height: 160px;
    border-top: 1px solid var(--border-color);
    background: #090c14;
    display: flex;
    flex-direction: column;
}

.output-header {
    padding: 0.4rem 1rem;
    background: rgba(255, 255, 255, 0.03);
    color: var(--text-secondary);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 700;
}

#code-output {
    padding: 0.85rem 1rem;
    color: #cbd5e1;
    font-family: 'Consolas', monospace;
    font-size: 0.88rem;
    overflow-y: auto;
    flex: 1;
    white-space: pre-wrap;
    line-height: 1.5;
}

/* Footer */
footer {
    background: #080b12;
    border-top: 1px solid var(--border-color);
    padding: 2.5rem 2rem 1.5rem;
    margin-top: auto;
}

.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 2rem;
}

@media (max-width: 768px) {
    .footer-inner {
        grid-template-columns: 1fr;
    }
    .container {
        flex-direction: column;
    }
    .sidebar {
        width: 100%;
        max-height: 300px;
    }
}

.footer-col h4, .footer-col h5 {
    color: var(--text-primary);
    margin-bottom: 0.85rem;
    font-size: 1rem;
}

.footer-col ul {
    list-style: none;
}

.footer-col li {
    margin-bottom: 6px;
}

.footer-col a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    transition: var(--transition);
}

.footer-col a:hover {
    color: var(--accent-color);
}

.footer-bottom {
    text-align: center;
    padding-top: 1.5rem;
    margin-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.05);
    color: var(--text-secondary);
    font-size: 0.82rem;
}