/**
 * Base CSS - Reset, Typography, Colors
 * D-13: Custom CSS (no Tailwind/Bootstrap)
 * D-14: Split CSS files for organization
 */

/* ========== CSS Variables ========== */
:root {
    /* Color Palette */
    --primary-blue: #1a56db;
    --secondary-blue: #3b82f6;
    --dark-blue: #1e3a5f;
    --accent-orange: #f59e0b;

    /* Text Colors */
    --text-dark: #1f2937;
    --text-gray: #6b7280;
    --text-light: #9ca3af;

    /* Background Colors */
    --bg-light: #f9fafb;
    --bg-white: #ffffff;

    /* Shadows */
    --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);

    /* Typography */
    --font-sans: "Source Han Sans SC", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-en: "Inter", "Roboto", -apple-system, BlinkMacSystemFont, sans-serif;

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;

    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
    --transition-slow: 500ms ease;

    /* Header Height */
    --header-height: 70px;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-light);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Language-specific font */
[lang="en"],
[lang="en-US"] {
    font-family: var(--font-en);
}

/* ========== Typography ========== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    color: var(--text-dark);
    margin-bottom: var(--spacing-md);
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.875rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: var(--spacing-md);
}

a {
    color: var(--primary-blue);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--secondary-blue);
}

strong, b {
    font-weight: 600;
}

small {
    font-size: 0.875rem;
}

/* ========== Lists ========== */
ul, ol {
    list-style: none;
}

/* ========== Images ========== */
img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ========== Forms ========== */
button,
input,
select,
textarea {
    font-family: inherit;
    font-size: inherit;
    line-height: inherit;
}

button {
    cursor: pointer;
    border: none;
    background: none;
}

input:focus,
select:focus,
textarea:focus,
button:focus {
    outline: 2px solid var(--primary-blue);
    outline-offset: 2px;
}

/* ========== Tables ========== */
table {
    width: 100%;
    border-collapse: collapse;
}

/* ========== Utility Classes ========== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }
.mt-4 { margin-top: var(--spacing-xl); }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-sm); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mb-3 { margin-bottom: var(--spacing-lg); }
.mb-4 { margin-bottom: var(--spacing-xl); }

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

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