/* ===========================
   CSS Variables & Root Styles
   =========================== */
:root {
    /* Primary Colors */
    --color-primary: #667eea;
    --color-primary-dark: #5568d3;
    --color-primary-light: #7c94f5;
    
    /* Secondary Colors */
    --color-secondary: #764ba2;
    --color-accent: #FF6B6B;
    --color-accent-light: #FFE66D;
    
    /* Semantic Colors */
    --color-success: #4CAF50;
    --color-warning: #FF9800;
    --color-danger: #F44336;
    --color-info: #2196F3;
    
    /* Neutrals */
    --color-bg-light: #F5F7FA;
    --color-bg-white: #FFFFFF;
    --color-text-dark: #212121;
    --color-text-secondary: #757575;
    --color-text-light: #BDBDBD;
    --color-border: #E0E0E0;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-accent: linear-gradient(135deg, #FF6B6B 0%, #FFE66D 100%);
    --gradient-success: linear-gradient(135deg, #4CAF50 0%, #81C784 100%);
    
    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.15);
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.2);
    --shadow-xl: 0 20px 60px rgba(0,0,0,0.3);
    
    /* Spacing */
    --spacing-xs: 8px;
    --spacing-sm: 12px;
    --spacing-md: 20px;
    --spacing-lg: 30px;
    --spacing-xl: 40px;
    
    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-full: 50%;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* Typography */
    --font-family-base: 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;
}

/* ===========================
   Base Styles
   =========================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family-base);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text-dark);
    background: var(--gradient-primary);
    min-height: 100vh;
    overflow-x: hidden;
}

/* ===========================
   Layout Components
   =========================== */
.app-container {
    width: 100%;
    min-height: 100vh;
}

.app-header {
    background: white;
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 0;
    z-index: 100;
    animation: slideDown 0.6s ease-out;
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-md) var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-section {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.app-logo {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
}

.header-text h1 {
    font-size: var(--font-size-2xl);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 4px;
}

.header-text p {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}

.user-section {
    display: flex;
    gap: var(--spacing-sm);
}

.btn-icon {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--gradient-primary);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-sm);
}

.btn-icon:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-icon .icon {
    font-size: var(--font-size-xl);
}

/* ===========================
   Main Content
   =========================== */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-lg);
}

.welcome-section {
    margin-bottom: var(--spacing-xl);
    animation: fadeIn 0.6s ease-out;
}

.welcome-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    text-align: center;
}

.welcome-card h2 {
    font-size: var(--font-size-3xl);
    color: var(--color-primary);
    margin-bottom: var(--spacing-md);
}

.welcome-card p {
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
}

/* ===========================
   Filter Section
   =========================== */
.filter-section {
    margin-bottom: var(--spacing-xl);
    animation: fadeIn 0.8s ease-out;
}

.search-container {
    position: relative;
    margin-bottom: var(--spacing-md);
}

.search-input {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-xl) var(--spacing-md) 50px;
    font-size: var(--font-size-lg);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: white;
    transition: all var(--transition-base);
}

.search-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.search-icon {
    position: absolute;
    left: var(--spacing-md);
    top: 50%;
    transform: translateY(-50%);
    font-size: var(--font-size-xl);
    pointer-events: none;
}

.filter-buttons {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.filter-btn {
    padding: var(--spacing-sm) var(--spacing-md);
    background: white;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text-dark);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-base);
}

.filter-btn:hover {
    border-color: var(--color-primary);
    background: rgba(102, 126, 234, 0.05);
}

.filter-btn.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
}

/* ===========================
   Units Grid
   =========================== */
.modules-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: var(--spacing-lg);
    animation: fadeIn 1s ease-out;
}

.module-card {
    background: white;
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.module-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 6px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.module-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.module-card:hover::before {
    opacity: 1;
}

.module-card.active {
    border: 2px solid var(--color-primary);
}

.module-card.active::before {
    opacity: 1;
    height: 8px;
}

.module-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.module-content h3 {
    font-size: var(--font-size-xl);
    color: var(--color-text-dark);
    margin-bottom: var(--spacing-sm);
}

.module-content p {
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.5;
}

.module-meta {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    margin-bottom: var(--spacing-md);
}

.strand-badge, .status-badge {
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    font-size: var(--font-size-xs);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.strand-badge.number {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
}

.strand-badge.geometry {
    background: linear-gradient(135deg, #4CAF50, #81C784);
    color: white;
}

.strand-badge.statistics {
    background: linear-gradient(135deg, #FF9800, #FFB74D);
    color: white;
}

.status-badge.available {
    background: linear-gradient(135deg, #4CAF50, #81C784);
    color: white;
    animation: pulse 2s infinite;
}

.status-badge.coming-soon {
    background: var(--color-bg-light);
    color: var(--color-text-secondary);
    border: 1px solid var(--color-border);
}

.module-progress {
    margin-top: var(--spacing-md);
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--color-bg-light);
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-bottom: var(--spacing-xs);
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width var(--transition-slow);
}

.progress-text {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    font-weight: 600;
}

/* ===========================
   Modal
   =========================== */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    animation: fadeIn var(--transition-base);
}

.modal.active {
    display: flex;
}

.modal-content {
    background: white;
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-xl);
    animation: slideUp 0.4s ease-out;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg);
    border-bottom: 2px solid var(--color-bg-light);
}

.modal-header h2 {
    font-size: var(--font-size-2xl);
    color: var(--color-primary);
}

.close-btn {
    width: 40px;
    height: 40px;
    border: none;
    background: var(--color-bg-light);
    border-radius: var(--radius-full);
    font-size: var(--font-size-2xl);
    cursor: pointer;
    transition: all var(--transition-base);
    display: flex;
    align-items: center;
    justify-content: center;
}

.close-btn:hover {
    background: var(--color-danger);
    color: white;
}

.modal-body {
    padding: var(--spacing-lg);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.stat-card {
    background: var(--gradient-primary);
    color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    text-align: center;
    box-shadow: var(--shadow-sm);
}

.stat-icon {
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-sm);
}

.stat-value {
    font-size: var(--font-size-3xl);
    font-weight: bold;
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    font-size: var(--font-size-sm);
    opacity: 0.9;
}

.achievements-section h3 {
    color: var(--color-text-dark);
    margin-bottom: var(--spacing-md);
    font-size: var(--font-size-xl);
}

.achievements-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.empty-state {
    text-align: center;
    color: var(--color-text-secondary);
    padding: var(--spacing-xl);
    font-style: italic;
}

/* ===========================
   Animations
   =========================== */
@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.7;
    }
}

@keyframes shake {
    0%, 100% {
        transform: translateX(0);
    }
    25% {
        transform: translateX(-10px);
    }
    75% {
        transform: translateX(10px);
    }
}

/* ===========================
   Utility Classes
   =========================== */
.hidden {
    display: none !important;
}

.text-center {
    text-align: center;
}

.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }

.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }

.p-1 { padding: var(--spacing-xs); }
.p-2 { padding: var(--spacing-sm); }
.p-3 { padding: var(--spacing-md); }
.p-4 { padding: var(--spacing-lg); }