/**
 * Design System - CSS Variables & Standards
 * Chuẩn hóa typography, spacing, colors, breakpoints
 */

:root {
    /* === COLORS === */
    /* Primary Colors */
    --color-primary: #0066cc;
    --color-primary-dark: #0052a3;
    --color-primary-light: #3385d6;
    
    /* Secondary Colors */
    --color-secondary: #28a745;
    --color-secondary-dark: #218838;
    --color-secondary-light: #48b461;
    
    /* Accent Colors */
    --color-accent: #ff9900;
    --color-accent-dark: #e68a00;
    
    /* Neutral Colors */
    --color-text-primary: #333333;
    --color-text-secondary: #666666;
    --color-text-muted: #999999;
    --color-text-light: #cccccc;
    
    /* Background Colors */
    --color-bg-primary: #ffffff;
    --color-bg-secondary: #f8f9fa;
    --color-bg-tertiary: #e9ecef;
    --color-bg-dark: #343a40;
    
    /* Border Colors */
    --color-border-light: #e9ecef;
    --color-border-medium: #dee2e6;
    --color-border-dark: #ced4da;
    
    /* Status Colors */
    --color-success: #28a745;
    --color-warning: #ffc107;
    --color-error: #dc3545;
    --color-info: #17a2b8;
    
    /* Gradient */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    
    /* === TYPOGRAPHY === */
    /* Font Families */
    --font-primary: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-monospace: "Courier New", Courier, monospace;
    
    /* Font Sizes */
    --font-size-xs: 0.75rem;    /* 12px */
    --font-size-sm: 0.875rem;   /* 14px */
    --font-size-base: 1rem;     /* 16px */
    --font-size-lg: 1.125rem;   /* 18px */
    --font-size-xl: 1.25rem;    /* 20px */
    --font-size-2xl: 1.5rem;    /* 24px */
    --font-size-3xl: 1.875rem;  /* 30px */
    --font-size-4xl: 2.25rem;   /* 36px */
    
    /* Font Weights */
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    
    /* Line Heights */
    --line-height-tight: 1.2;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
    
    /* === SPACING === */
    /* Spacing Scale (8px base) */
    --space-0: 0;
    --space-1: 0.25rem;  /* 4px */
    --space-2: 0.5rem;   /* 8px */
    --space-3: 0.75rem;  /* 12px */
    --space-4: 1rem;     /* 16px */
    --space-5: 1.25rem;  /* 20px */
    --space-6: 1.5rem;   /* 24px */
    --space-8: 2rem;     /* 32px */
    --space-10: 2.5rem;  /* 40px */
    --space-12: 3rem;    /* 48px */
    --space-16: 4rem;    /* 64px */
    
    /* === BORDERS === */
    --border-radius-sm: 0.25rem;   /* 4px */
    --border-radius-base: 0.5rem;  /* 8px */
    --border-radius-lg: 0.75rem;   /* 12px */
    --border-radius-xl: 1rem;      /* 16px */
    --border-radius-full: 9999px;
    
    --border-width-thin: 1px;
    --border-width-base: 2px;
    --border-width-thick: 4px;
    
    /* === SHADOWS === */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-base: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 8px 20px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 12px 28px rgba(0, 0, 0, 0.2);
    
    /* === TRANSITIONS === */
    --transition-fast: 150ms ease;
    --transition-base: 300ms ease;
    --transition-slow: 500ms 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;
    
    /* === BREAKPOINTS === */
    /* Sử dụng trong media queries */
    --breakpoint-xs: 0;
    --breakpoint-sm: 576px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 992px;
    --breakpoint-xl: 1200px;
    --breakpoint-xxl: 1400px;
}

/* === UTILITY CLASSES === */

/* Typography Utilities */
.text-xs { font-size: var(--font-size-xs); }
.text-sm { font-size: var(--font-size-sm); }
.text-base { font-size: var(--font-size-base); }
.text-lg { font-size: var(--font-size-lg); }
.text-xl { font-size: var(--font-size-xl); }
.text-2xl { font-size: var(--font-size-2xl); }

.font-normal { font-weight: var(--font-weight-normal); }
.font-medium { font-weight: var(--font-weight-medium); }
.font-semibold { font-weight: var(--font-weight-semibold); }
.font-bold { font-weight: var(--font-weight-bold); }

.leading-tight { line-height: var(--line-height-tight); }
.leading-normal { line-height: var(--line-height-normal); }
.leading-relaxed { line-height: var(--line-height-relaxed); }

/* Color Utilities */
.text-primary { color: var(--color-text-primary); }
.text-secondary { color: var(--color-text-secondary); }
.text-muted { color: var(--color-text-muted); }

.bg-primary { background-color: var(--color-bg-primary); }
.bg-secondary { background-color: var(--color-bg-secondary); }

/* Spacing Utilities */
.p-0 { padding: var(--space-0); }
.p-2 { padding: var(--space-2); }
.p-4 { padding: var(--space-4); }
.p-6 { padding: var(--space-6); }
.p-8 { padding: var(--space-8); }

.m-0 { margin: var(--space-0); }
.m-2 { margin: var(--space-2); }
.m-4 { margin: var(--space-4); }
.m-6 { margin: var(--space-6); }
.m-8 { margin: var(--space-8); }

/* === ACCESSIBILITY === */

/* Focus States */
*:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Skip to content link */
.skip-to-content {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--color-primary);
    color: white;
    padding: var(--space-2) var(--space-4);
    text-decoration: none;
    z-index: var(--z-tooltip);
}

.skip-to-content:focus {
    top: 0;
}

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

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --color-primary: #0052a3;
        --color-text-primary: #000000;
        --color-bg-primary: #ffffff;
    }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* === RESPONSIVE HELPERS === */
@media (max-width: 767px) {
    .hide-mobile { display: none !important; }
}

@media (min-width: 768px) {
    .hide-desktop { display: none !important; }
}