@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

:root {
    --primary-color: #0F172A;
    --primary-light: #1E293B;
    --secondary-color: #3B82F6;
    --accent-color: #10B981;
    --bg-color: #F8FAFC;
    --card-bg: #FFFFFF;
    --text-color: #334155;
    --text-muted: #64748B;
    --border-color: #E2E8F0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-md: 8px;
    --radius-lg: 12px;
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

/* App Layout Structure */
.app-container {
    display: flex;
    min-height: 100vh;
    overflow: hidden;
}

/* Sidebar Styles */
.sidebar {
    width: 280px;
    background-color: var(--card-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    position: fixed;
    height: 100vh;
    z-index: 100;
    box-shadow: var(--shadow-sm);
    transition: transform 0.3s ease;
}

.sidebar-header {
    padding: 24px 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.sidebar-header h2 {
    font-size: 1.25rem;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 8px;
}

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

/* Progress Indicator */
.progress-container {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
}

.progress-text {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-weight: 500;
    margin-bottom: 8px;
}

.progress-bar-bg {
    width: 100%;
    height: 6px;
    background-color: var(--border-color);
    border-radius: 10px;
    overflow: hidden;
}

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

/* Nav links */
.sidebar-nav {
    flex-grow: 1;
    overflow-y: auto;
    padding: 15px 10px;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 15px;
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    border-radius: var(--radius-md);
    margin-bottom: 6px;
    transition: background 0.2s, color 0.2s;
}

.nav-link i {
    font-size: 1.2rem;
    color: var(--text-muted);
    transition: color 0.2s;
}

.nav-link:hover {
    background-color: var(--border-color);
}

.nav-link.active {
    background-color: #EFF6FF;
    color: var(--secondary-color);
    pointer-events: none;
}

.nav-link.active i {
    color: var(--secondary-color);
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--border-color);
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* Main Content Area */
.main-content {
    flex-grow: 1;
    margin-left: 280px;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    background-color: var(--bg-color);
}

.mobile-header {
    display: none;
    background: var(--card-bg);
    padding: 15px 20px;
    border-bottom: 1px solid var(--border-color);
    align-items: center;
    gap: 15px;
    position: sticky;
    top: 0;
    z-index: 50;
    box-shadow: var(--shadow-sm);
}

.toggle-sidebar-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--primary-color);
}

.content-wrapper {
    max-width: 1000px;
    margin: 0 auto;
    width: 100%;
    padding: 30px;
    flex-grow: 1;
}

/* Data Overview Section */
.data-preview-section {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    padding: 20px;
    margin-bottom: 30px;
    border: 1px solid var(--border-color);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.section-header h4 {
    font-size: 1.1rem;
    color: var(--primary-light);
    display: flex;
    align-items: center;
    gap: 8px;
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--border-color);
    padding: 6px 12px;
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    cursor: pointer;
    font-weight: 500;
    color: var(--text-muted);
    transition: all 0.2s;
}

.btn-outline:hover {
    background: var(--border-color);
    color: var(--text-color);
}

/* Table container styling */
.table-container {
    margin-top: 15px;
    overflow-x: auto;
    transition: max-height 0.4s ease;
}

.table-container.hidden {
    display: none;
}

table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
}

th {
    background: var(--bg-color);
    color: var(--text-muted);
    text-transform: uppercase;
    font-weight: 600;
    font-size: 0.75rem;
    padding: 12px 15px;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
}

th:hover {
    background: #E2E8F0;
}

td {
    padding: 12px 15px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-color);
}

tbody tr {
    transition: background 0.2s;
}

tbody tr:hover {
    background-color: #EFF6FF;
}

.highlight-row {
    background-color: #FEF3C7 !important;
}

/* Session Content Area Styles */
.session-content {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: 40px;
    min-height: 400px;
    animation: fadeInContent 0.4s ease forwards;
    position: relative;
    border: 1px solid var(--border-color);
}

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

.session-badge {
    display: inline-block;
    background: #EFF6FF;
    color: var(--secondary-color);
    padding: 5px 12px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    margin-bottom: 15px;
}

.session-title {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: 25px;
    line-height: 1.2;
}

.objective-list {
    background: #F8FAFC;
    padding: 20px 25px;
    border-left: 4px solid var(--secondary-color);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    margin-bottom: 30px;
}

.objective-list h4 {
    margin-bottom: 10px;
    color: var(--primary-light);
    display: flex;
    align-items: center;
    gap: 8px;
}

.objective-list ul {
    list-style-position: inside;
    color: var(--text-muted);
}

.explanation {
    margin-bottom: 30px;
    font-size: 1.05rem;
}

/* Interactive Section */
.interactive-zone {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 25px;
    background: #FAFAF9;
    margin-bottom: 30px;
}

.interactive-header {
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 15px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.actions-row {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 20px;
}

.btn-action {
    background: var(--secondary-color);
    color: #fff;
    border: none;
    padding: 10px 18px;
    border-radius: var(--radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.btn-action:hover {
    background: #2563EB;
}

.btn-action:active {
    transform: scale(0.98);
}

.btn-success {
    background: var(--accent-color);
}

.btn-success:hover {
    background: #059669;
}

.result-box {
    background: #fff;
    padding: 15px;
    border-radius: var(--radius-md);
    border: 1px dashed var(--border-color);
    font-family: monospace;
    font-size: 1.1rem;
    color: var(--primary-color);
    min-height: 50px;
    display: flex;
    align-items: center;
}

.result-box.empty {
    color: var(--text-muted);
    font-style: italic;
    font-family: inherit;
    font-size: 0.95rem;
}

/* Assignment Styles */
.assignment-box {
    background: #FFFBEB;
    border: 1px solid #FDE68A;
    border-radius: var(--radius-md);
    padding: 25px;
    margin-top: 40px;
}

.assignment-box h4 {
    color: #B45309;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Input Fields */
.input-control {
    padding: 10px 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.95rem;
}

.input-control:focus {
    outline: none;
    border-color: var(--secondary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

/* Bottom Navigation */
.bottom-nav {
    display: flex;
    justify-content: space-between;
    margin-top: 30px;
}

.nav-btn {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    padding: 12px 20px;
    border-radius: var(--radius-md);
    font-weight: 600;
    cursor: pointer;
    color: var(--primary-color);
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all 0.2s;
}

.nav-btn:hover:not(:disabled) {
    background: #F1F5F9;
}

.nav-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    background: #F8FAFC;
}

/* Power Query Simulation Styles */
.step-container {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
}
.step-circle {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background: var(--border-color);
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    transition: all 0.3s;
}
.step-circle.active {
    background: var(--secondary-color);
    color: #fff;
}
.step-content {
    background: white;
    padding: 10px 15px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    flex-grow: 1;
    color: var(--text-muted);
}
.step-content.active {
    color: var(--primary-color);
    border-color: var(--secondary-color);
    box-shadow: var(--shadow-sm);
}

/* Mobile Responsive Overlay */
.sidebar-overlay {
    display: none;
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.5);
    z-index: 90;
    backdrop-filter: blur(2px);
}

@media (max-width: 900px) {
    .sidebar {
        transform: translateX(-100%);
    }
    
    .sidebar.open {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .mobile-header {
        display: flex;
    }
    
    .close-sidebar-btn {
        display: block;
    }
    
    .sidebar-overlay.active {
        display: block;
    }

    .content-wrapper {
        padding: 20px;
    }
    
    .session-title {
        font-size: 1.5rem;
    }
    
    .session-content {
        padding: 20px;
    }
}