/* ===== CSS RESET & BASE ===== */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    transition: all 0.3s ease;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ===== CSS VARIABLES ===== */
:root {
    /* Primary Colors */
    --primary-blue: #3B82F6;
    --primary-dark: #1E40AF;
    --primary-light: #DBEAFE;
    
    /* Accent Colors */
    --accent-green: #10B981;
    --accent-red: #EF4444;
    --accent-orange: #F59E0B;
    --accent-purple: #8B5CF6;
    
    /* Neutral Colors */
    --neutral-dark: #1F2937;
    --neutral-medium: #6B7280;
    --neutral-light: #F9FAFB;
    
    /* Semantic Colors - Light Mode */
    --bg-primary: #FFFFFF;
    --bg-secondary: #F8FAFC;
    --bg-tertiary: #F1F5F9;
    --text-primary: #1E293B;
    --text-secondary: #64748B;
    --text-muted: #94A3B8;
    --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);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Typography */
    --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: 1.875rem;
    --font-size-4xl: 2.25rem;
    --font-size-5xl: 3rem;
    --font-size-6xl: 3.75rem;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 200ms ease;
    --transition-slow: 300ms ease;
    
    /* Z-index */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-fixed: 1030;
    --z-modal-backdrop: 1040;
    --z-modal: 1050;
    --z-popover: 1060;
    --z-tooltip: 1070;
}

/* Dark Mode Variables */
.dark-mode {
    --bg-primary: #0F172A;
    --bg-secondary: #1E293B;
    --bg-tertiary: #334155;
    --text-primary: #F1F5F9;
    --text-secondary: #CBD5E1;
    --text-muted: #94A3B8;
    --border-color: #334155;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 10px 10px -5px rgba(0, 0, 0, 0.3);
}

/* ===== UTILITY CLASSES ===== */
.hidden {
    display: none !important;
}

.invisible {
    visibility: hidden !important;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

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

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

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

.flex {
    display: flex;
}

.flex-col {
    flex-direction: column;
}

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

.justify-center {
    justify-content: center;
}

.justify-between {
    justify-content: space-between;
}

.gap-sm {
    gap: var(--spacing-sm);
}

.gap-md {
    gap: var(--spacing-md);
}

.gap-lg {
    gap: var(--spacing-lg);
}

/* ===== LOADING SCREEN ===== */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--bg-primary);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: var(--z-modal);
    transition: opacity var(--transition-slow);
}

.loading-screen.fade-out {
    opacity: 0;
    pointer-events: none;
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 4px solid var(--border-color);
    border-top: 4px solid var(--primary-blue);
    border-radius: var(--radius-full);
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing-lg);
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.loading-screen h2 {
    color: var(--text-secondary);
    font-size: var(--font-size-lg);
    font-weight: 400;
}

/* ===== APP CONTAINER ===== */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
}

/* ===== HEADER ===== */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: var(--z-sticky);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-lg);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--text-primary);
}

.logo i {
    width: 28px;
    height: 28px;
    color: var(--primary-blue);
}

.logo h1 {
    font-size: var(--font-size-xl);
    margin: 0;
}

/* ===== NAVIGATION TABS ===== */
.nav-tabs {
    display: flex;
    gap: var(--spacing-xs);
    background: var(--bg-secondary);
    padding: var(--spacing-xs);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.nav-tab {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: var(--font-size-sm);
    font-weight: 500;
    text-decoration: none;
    white-space: nowrap;
}

.nav-tab:hover {
    color: var(--text-primary);
    background: var(--bg-tertiary);
}

.nav-tab.active {
    background: var(--primary-blue);
    color: white;
    box-shadow: var(--shadow-sm);
}

.nav-tab i {
    width: 16px;
    height: 16px;
}

.nav-tab span {
    display: none;
}

/* ===== HEADER ACTIONS ===== */
.header-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.btn-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn-icon:hover {
    color: var(--text-primary);
    background: var(--bg-tertiary);
    border-color: var(--primary-blue);
}

.btn-icon i {
    width: 18px;
    height: 18px;
}

/* ===== MAIN CONTENT ===== */
.main-content {
    flex: 1;
    padding: var(--spacing-xl) 0;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
    padding-left: var(--spacing-lg);
    padding-right: var(--spacing-lg);
}

/* ===== TAB CONTENT ===== */
.tab-content {
    display: none;
    animation: fadeIn var(--transition-normal);
}

.tab-content.active {
    display: block;
}

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

/* ===== SECTION HEADER ===== */
.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
}

.section-header h2 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-2xl);
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
}

.section-header h2 i {
    width: 28px;
    height: 28px;
    color: var(--primary-blue);
}

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

/* ===== RESPONSIVE DESIGN ===== */
@media (min-width: 768px) {
    .nav-tab span {
        display: inline;
    }
    
    .header-content {
        padding: 0 var(--spacing-xl);
    }
    
    .main-content {
        padding-left: var(--spacing-xl);
        padding-right: var(--spacing-xl);
    }
}

@media (max-width: 767px) {
    .header-content {
        flex-wrap: wrap;
        gap: var(--spacing-md);
    }
    
    .nav-tabs {
        order: 3;
        width: 100%;
        justify-content: space-between;
    }
    
    .nav-tab {
        flex: 1;
        justify-content: center;
        padding: var(--spacing-sm);
    }
    
    .section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-md);
    }
    
    .section-controls {
        width: 100%;
        justify-content: flex-end;
    }
}

@media (max-width: 480px) {
    .header-content {
        padding: 0 var(--spacing-md);
    }
    
    .main-content {
        padding: var(--spacing-lg) var(--spacing-md);
    }
    
    .logo h1 {
        display: none;
    }
    
    .header-actions {
        gap: var(--spacing-xs);
    }
}