Practical Visual Design Implementation

/* CSS Color System Implementation */
:root {
    /* Primary Color Palette */
    --primary-50: #eff6ff;
    --primary-100: #dbeafe;
    --primary-200: #bfdbfe;
    --primary-300: #93c5fd;
    --primary-400: #60a5fa;
    --primary-500: #3b82f6;
    --primary-600: #2563eb;
    --primary-700: #1d4ed8;
    --primary-800: #1e40af;
    --primary-900: #1e3a8a;
    
    /* Neutral Color Palette */
    --neutral-50: #fafafa;
    --neutral-100: #f5f5f5;
    --neutral-200: #e5e5e5;
    --neutral-300: #d4d4d4;
    --neutral-400: #a3a3a3;
    --neutral-500: #737373;
    --neutral-600: #525252;
    --neutral-700: #404040;
    --neutral-800: #262626;
    --neutral-900: #171717;
    
    /* Semantic Colors */
    --success-500: #10b981;
    --warning-500: #f59e0b;
    --error-500: #ef4444;
    --info-500: #3b82f6;
}

/* Color Utility Classes */
.bg-primary-500 { background-color: var(--primary-500); }
.bg-primary-600 { background-color: var(--primary-600); }
.text-primary-500 { color: var(--primary-500); }
.text-primary-600 { color: var(--primary-600); }

.bg-neutral-50 { background-color: var(--neutral-50); }
.bg-neutral-100 { background-color: var(--neutral-100); }
.text-neutral-900 { color: var(--neutral-900); }
.text-neutral-600 { color: var(--neutral-600); }

/* Semantic Color Classes */
.bg-success { background-color: var(--success-500); }
.bg-warning { background-color: var(--warning-500); }
.bg-error { background-color: var(--error-500); }
.bg-info { background-color: var(--info-500); }

.text-success { color: var(--success-500); }
.text-warning { color: var(--warning-500); }
.text-error { color: var(--error-500); }
.text-info { color: var(--info-500); }

/* Color Contrast Utilities */
.text-high-contrast { color: var(--neutral-900); }
.text-medium-contrast { color: var(--neutral-600); }
.text-low-contrast { color: var(--neutral-400); }

/* Interactive Color States */
.btn-primary {
    background-color: var(--primary-500);
    color: white;
    transition: background-color 0.2s ease;
}

.btn-primary:hover {
    background-color: var(--primary-600);
}

.btn-primary:active {
    background-color: var(--primary-700);
}

/* Color Accessibility */
@media (prefers-color-scheme: dark) {
    :root {
        --neutral-50: #171717;
        --neutral-100: #262626;
        --neutral-900: #fafafa;
        --neutral-600: #a3a3a3;
    }
}

/* Typography System Implementation */
:root {
    /* Font Families */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-serif: 'Georgia', 'Times New Roman', serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
    
    /* Font Sizes - Modular Scale (1.25 ratio) */
    --text-xs: 0.75rem;    /* 12px */
    --text-sm: 0.875rem;   /* 14px */
    --text-base: 1rem;     /* 16px */
    --text-lg: 1.125rem;   /* 18px */
    --text-xl: 1.25rem;    /* 20px */
    --text-2xl: 1.5rem;    /* 24px */
    --text-3xl: 1.875rem;  /* 30px */
    --text-4xl: 2.25rem;   /* 36px */
    --text-5xl: 3rem;      /* 48px */
    --text-6xl: 3.75rem;   /* 60px */
    
    /* Line Heights */
    --leading-none: 1;
    --leading-tight: 1.25;
    --leading-snug: 1.375;
    --leading-normal: 1.5;
    --leading-relaxed: 1.625;
    --leading-loose: 2;
    
    /* Font Weights */
    --font-thin: 100;
    --font-extralight: 200;
    --font-light: 300;
    --font-normal: 400;
    --font-medium: 500;
    --font-semibold: 600;
    --font-bold: 700;
    --font-extrabold: 800;
    --font-black: 900;
    
    /* Letter Spacing */
    --tracking-tighter: -0.05em;
    --tracking-tight: -0.025em;
    --tracking-normal: 0em;
    --tracking-wide: 0.025em;
    --tracking-wider: 0.05em;
    --tracking-widest: 0.1em;
}

/* Typography Utility Classes */
.text-xs { font-size: var(--text-xs); line-height: var(--leading-normal); }
.text-sm { font-size: var(--text-sm); line-height: var(--leading-normal); }
.text-base { font-size: var(--text-base); line-height: var(--leading-normal); }
.text-lg { font-size: var(--text-lg); line-height: var(--leading-relaxed); }
.text-xl { font-size: var(--text-xl); line-height: var(--leading-relaxed); }
.text-2xl { font-size: var(--text-2xl); line-height: var(--leading-tight); }
.text-3xl { font-size: var(--text-3xl); line-height: var(--leading-tight); }
.text-4xl { font-size: var(--text-4xl); line-height: var(--leading-tight); }
.text-5xl { font-size: var(--text-5xl); line-height: var(--leading-tight); }
.text-6xl { font-size: var(--text-6xl); line-height: var(--leading-tight); }

/* Font Weight Classes */
.font-thin { font-weight: var(--font-thin); }
.font-light { font-weight: var(--font-light); }
.font-normal { font-weight: var(--font-normal); }
.font-medium { font-weight: var(--font-medium); }
.font-semibold { font-weight: var(--font-semibold); }
.font-bold { font-weight: var(--font-bold); }
.font-extrabold { font-weight: var(--font-extrabold); }

/* Font Family Classes */
.font-sans { font-family: var(--font-sans); }
.font-serif { font-family: var(--font-serif); }
.font-mono { font-family: var(--font-mono); }

/* Letter Spacing Classes */
.tracking-tighter { letter-spacing: var(--tracking-tighter); }
.tracking-tight { letter-spacing: var(--tracking-tight); }
.tracking-normal { letter-spacing: var(--tracking-normal); }
.tracking-wide { letter-spacing: var(--tracking-wide); }
.tracking-wider { letter-spacing: var(--tracking-wider); }
.tracking-widest { letter-spacing: var(--tracking-widest); }

/* Typography Hierarchy */
.heading-1 {
    font-size: var(--text-4xl);
    font-weight: var(--font-bold);
    line-height: var(--leading-tight);
    letter-spacing: var(--tracking-tight);
    font-family: var(--font-sans);
}

.heading-2 {
    font-size: var(--text-3xl);
    font-weight: var(--font-semibold);
    line-height: var(--leading-tight);
    letter-spacing: var(--tracking-tight);
}

.heading-3 {
    font-size: var(--text-2xl);
    font-weight: var(--font-semibold);
    line-height: var(--leading-tight);
}

.body-large {
    font-size: var(--text-lg);
    line-height: var(--leading-relaxed);
    font-weight: var(--font-normal);
}

.body {
    font-size: var(--text-base);
    line-height: var(--leading-normal);
    font-weight: var(--font-normal);
}

.body-small {
    font-size: var(--text-sm);
    line-height: var(--leading-normal);
    font-weight: var(--font-normal);
}

.caption {
    font-size: var(--text-xs);
    line-height: var(--leading-normal);
    font-weight: var(--font-medium);
    text-transform: uppercase;
    letter-spacing: var(--tracking-wide);
}

/* Responsive Typography */
@media (max-width: 768px) {
    .heading-1 { font-size: var(--text-3xl); }
    .heading-2 { font-size: var(--text-2xl); }
    .heading-3 { font-size: var(--text-xl); }
    .body-large { font-size: var(--text-base); }
}

/* Typography Accessibility */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* CSS Grid System Implementation */
:root {
    /* Grid Breakpoints */
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;
    --breakpoint-xl: 1280px;
    --breakpoint-2xl: 1536px;
    
    /* Grid Columns */
    --grid-columns: 12;
    --grid-gutter: 1.5rem;
    --grid-margin: 1rem;
    
    /* Container Max Widths */
    --container-sm: 640px;
    --container-md: 768px;
    --container-lg: 1024px;
    --container-xl: 1280px;
    --container-2xl: 1536px;
}

/* Container System */
.container {
    width: 100%;
    margin-left: auto;
    margin-right: auto;
    padding-left: var(--grid-margin);
    padding-right: var(--grid-margin);
}

.container-sm {
    max-width: var(--container-sm);
}

.container-md {
    max-width: var(--container-md);
}

.container-lg {
    max-width: var(--container-lg);
}

.container-xl {
    max-width: var(--container-xl);
}

.container-2xl {
    max-width: var(--container-2xl);
}

/* Grid System */
.grid {
    display: grid;
    gap: var(--grid-gutter);
}

/* 12-Column Grid */
.grid-cols-12 {
    grid-template-columns: repeat(12, 1fr);
}

.col-span-1 { grid-column: span 1 / span 1; }
.col-span-2 { grid-column: span 2 / span 2; }
.col-span-3 { grid-column: span 3 / span 3; }
.col-span-4 { grid-column: span 4 / span 4; }
.col-span-5 { grid-column: span 5 / span 5; }
.col-span-6 { grid-column: span 6 / span 6; }
.col-span-7 { grid-column: span 7 / span 7; }
.col-span-8 { grid-column: span 8 / span 8; }
.col-span-9 { grid-column: span 9 / span 9; }
.col-span-10 { grid-column: span 10 / span 10; }
.col-span-11 { grid-column: span 11 / span 11; }
.col-span-12 { grid-column: span 12 / span 12; }

/* Responsive Grid Classes */
@media (min-width: 640px) {
    .sm\:col-span-1 { grid-column: span 1 / span 1; }
    .sm\:col-span-2 { grid-column: span 2 / span 2; }
    .sm\:col-span-3 { grid-column: span 3 / span 3; }
    .sm\:col-span-4 { grid-column: span 4 / span 4; }
    .sm\:col-span-6 { grid-column: span 6 / span 6; }
    .sm\:col-span-12 { grid-column: span 12 / span 12; }
}

@media (min-width: 768px) {
    .md\:col-span-1 { grid-column: span 1 / span 1; }
    .md\:col-span-2 { grid-column: span 2 / span 2; }
    .md\:col-span-3 { grid-column: span 3 / span 3; }
    .md\:col-span-4 { grid-column: span 4 / span 4; }
    .md\:col-span-6 { grid-column: span 6 / span 6; }
    .md\:col-span-8 { grid-column: span 8 / span 8; }
    .md\:col-span-12 { grid-column: span 12 / span 12; }
}

@media (min-width: 1024px) {
    .lg\:col-span-1 { grid-column: span 1 / span 1; }
    .lg\:col-span-2 { grid-column: span 2 / span 2; }
    .lg\:col-span-3 { grid-column: span 3 / span 3; }
    .lg\:col-span-4 { grid-column: span 4 / span 4; }
    .lg\:col-span-6 { grid-column: span 6 / span 6; }
    .lg\:col-span-8 { grid-column: span 8 / span 8; }
    .lg\:col-span-9 { grid-column: span 9 / span 9; }
    .lg\:col-span-12 { grid-column: span 12 / span 12; }
}

/* Grid Gap Utilities */
.gap-1 { gap: 0.25rem; }
.gap-2 { gap: 0.5rem; }
.gap-3 { gap: 0.75rem; }
.gap-4 { gap: 1rem; }
.gap-5 { gap: 1.25rem; }
.gap-6 { gap: 1.5rem; }
.gap-8 { gap: 2rem; }
.gap-10 { gap: 2.5rem; }
.gap-12 { gap: 3rem; }

/* Grid Row Utilities */
.grid-rows-1 { grid-template-rows: repeat(1, 1fr); }
.grid-rows-2 { grid-template-rows: repeat(2, 1fr); }
.grid-rows-3 { grid-template-rows: repeat(3, 1fr); }
.grid-rows-4 { grid-template-rows: repeat(4, 1fr); }
.grid-rows-5 { grid-template-rows: repeat(5, 1fr); }
.grid-rows-6 { grid-template-rows: repeat(6, 1fr); }

.row-span-1 { grid-row: span 1 / span 1; }
.row-span-2 { grid-row: span 2 / span 2; }
.row-span-3 { grid-row: span 3 / span 3; }
.row-span-4 { grid-row: span 4 / span 4; }
.row-span-5 { grid-row: span 5 / span 5; }
.row-span-6 { grid-row: span 6 / span 6; }

/* Grid Alignment */
.items-start { align-items: start; }
.items-center { align-items: center; }
.items-end { align-items: end; }
.items-stretch { align-items: stretch; }

.justify-start { justify-items: start; }
.justify-center { justify-items: center; }
.justify-end { justify-items: end; }
.justify-stretch { justify-items: stretch; }

/* Grid Content Alignment */
.content-start { align-content: start; }
.content-center { align-content: center; }
.content-end { align-content: end; }
.content-between { align-content: space-between; }
.content-around { align-content: space-around; }
.content-evenly { align-content: space-evenly; }

/* Grid Self Alignment */
.self-start { align-self: start; }
.self-center { align-self: center; }
.self-end { align-self: end; }
.self-stretch { align-self: stretch; }

/* Grid Justify Self */
.justify-self-start { justify-self: start; }
.justify-self-center { justify-self: center; }
.justify-self-end { justify-self: end; }
.justify-self-stretch { justify-self: stretch; }

/* Grid Areas */
.grid-areas {
    grid-template-areas: 
        "header header header"
        "sidebar main aside"
        "footer footer footer";
}

.header { grid-area: header; }
.sidebar { grid-area: sidebar; }
.main { grid-area: main; }
.aside { grid-area: aside; }
.footer { grid-area: footer; }

/* Responsive Grid Example */
.responsive-layout {
    display: grid;
    gap: 1rem;
    grid-template-columns: 1fr;
}

@media (min-width: 640px) {
    .responsive-layout {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1024px) {
    .responsive-layout {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (min-width: 1280px) {
    .responsive-layout {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* Visual Hierarchy Implementation */
:root {
    /* Z-Index Scale */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-fixed: 1030;
    --z-modal-backdrop: 1040;
    --z-modal: 1050;
    --z-popover: 1060;
    --z-tooltip: 1070;
    
    /* Shadow Scale */
    --shadow-xs: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-sm: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    --shadow-2xl: 0 25px 50px -12px rgb(0 0 0 / 0.25);
    
    /* Border Radius Scale */
    --radius-none: 0px;
    --radius-sm: 0.125rem;
    --radius-md: 0.375rem;
    --radius-lg: 0.5rem;
    --radius-xl: 0.75rem;
    --radius-2xl: 1rem;
    --radius-3xl: 1.5rem;
    --radius-full: 9999px;
}

/* Shadow Utilities */
.shadow-xs { box-shadow: var(--shadow-xs); }
.shadow-sm { box-shadow: var(--shadow-sm); }
.shadow-md { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }
.shadow-xl { box-shadow: var(--shadow-xl); }
.shadow-2xl { box-shadow: var(--shadow-2xl); }

/* Border Radius Utilities */
.rounded-none { border-radius: var(--radius-none); }
.rounded-sm { border-radius: var(--radius-sm); }
.rounded-md { border-radius: var(--radius-md); }
.rounded-lg { border-radius: var(--radius-lg); }
.rounded-xl { border-radius: var(--radius-xl); }
.rounded-2xl { border-radius: var(--radius-2xl); }
.rounded-3xl { border-radius: var(--radius-3xl); }
.rounded-full { border-radius: var(--radius-full); }

/* Z-Index Utilities */
.z-dropdown { z-index: var(--z-dropdown); }
.z-sticky { z-index: var(--z-sticky); }
.z-fixed { z-index: var(--z-fixed); }
.z-modal-backdrop { z-index: var(--z-modal-backdrop); }
.z-modal { z-index: var(--z-modal); }
.z-popover { z-index: var(--z-popover); }
.z-tooltip { z-index: var(--z-tooltip); }

/* Visual Hierarchy Components */
.card {
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--neutral-200);
    transition: all 0.2s ease;
}

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

.card-elevated {
    box-shadow: var(--shadow-lg);
}

.card-floating {
    box-shadow: var(--shadow-xl);
}

/* Button Hierarchy */
.btn-primary {
    background: var(--primary-500);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    box-shadow: var(--shadow-sm);
    transition: all 0.2s ease;
}

.btn-primary:hover {
    background: var(--primary-600);
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
}

.btn-secondary {
    background: var(--neutral-100);
    color: var(--neutral-700);
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    border: 1px solid var(--neutral-300);
    transition: all 0.2s ease;
}

.btn-secondary:hover {
    background: var(--neutral-200);
    border-color: var(--neutral-400);
}

/* Form Hierarchy */
.form-input {
    padding: 0.75rem;
    border: 1px solid var(--neutral-300);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: all 0.2s ease;
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-500);
    box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
}

.form-input.error {
    border-color: var(--error-500);
    box-shadow: 0 0 0 3px rgb(239 68 68 / 0.1);
}

/* Navigation Hierarchy */
.nav-primary {
    background: white;
    box-shadow: var(--shadow-sm);
    border-bottom: 1px solid var(--neutral-200);
    z-index: var(--z-sticky);
}

.nav-item {
    padding: 1rem;
    color: var(--neutral-600);
    transition: color 0.2s ease;
}

.nav-item:hover {
    color: var(--primary-600);
}

.nav-item.active {
    color: var(--primary-600);
    border-bottom: 2px solid var(--primary-500);
}

/* Modal Hierarchy */
.modal-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgb(0 0 0 / 0.5);
    z-index: var(--z-modal-backdrop);
}

.modal {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: white;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-2xl);
    z-index: var(--z-modal);
    max-width: 90vw;
    max-height: 90vh;
    overflow: auto;
}

/* Tooltip Hierarchy */
.tooltip {
    position: absolute;
    background: var(--neutral-900);
    color: white;
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    box-shadow: var(--shadow-lg);
    z-index: var(--z-tooltip);
    pointer-events: none;
}

.tooltip::before {
    content: '';
    position: absolute;
    top: -4px;
    left: 50%;
    transform: translateX(-50%);
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-bottom: 4px solid var(--neutral-900);
}

/* Responsive Hierarchy */
@media (max-width: 768px) {
    .card {
        border-radius: var(--radius-md);
        box-shadow: var(--shadow-xs);
    }
    
    .btn-primary,
    .btn-secondary {
        padding: 0.875rem 1.25rem;
        font-size: 1rem;
    }
    
    .modal {
        margin: 1rem;
        max-width: calc(100vw - 2rem);
        max-height: calc(100vh - 2rem);
    }
}