/* ============================================================
   Mastering Modern Online Dating — Stylesheet
   Color scheme: deep teal #1a6b8a | sky blue #3da5c5 | golden yellow #f7c948
   ============================================================ */

/* ===== CSS Variables ===== */
:root {
    --primary-color: #1a6b8a;
    --secondary-color: #3da5c5;
    --accent-color: #f7c948;
    --text-color: #2b2b2b;
    --text-light: #5a5a5a;
    --background: #ffffff;
    --background-alt: #f0f8fc;
    --border-color: #b8d9e8;
    --shadow: 0 2px 10px rgba(26, 107, 138, 0.10);
    --shadow-hover: 0 4px 20px rgba(26, 107, 138, 0.20);

    --font-main: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-heading: 'Georgia', 'Times New Roman', serif;

    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    --border-radius: 8px;
    --max-width: 800px;
}

/* ===== Dark Mode ===== */
@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #3da5c5;
        --secondary-color: #6dc8e0;
        --accent-color: #f7c948;
        --text-color: #e4e4e4;
        --text-light: #a8a8a8;
        --background: #141e24;
        --background-alt: #1c2d36;
        --border-color: #2e4d5f;
    }
}

/* ===== Base ===== */
*, *::before, *::after { box-sizing: border-box; }
html { font-size: 16px; scroll-behavior: smooth; }
body { font-family: var(--font-main); line-height: 1.75; color: var(--text-color); background: var(--background); margin: 0; padding: 0; }
.container { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--spacing-md); }

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 { font-family: var(--font-heading); line-height: 1.3; color: var(--primary-color); margin-top: var(--spacing-lg); margin-bottom: var(--spacing-sm); }
h1 { font-size: 2.6rem; margin-top: 0; }
h2 { font-size: 2rem; border-bottom: 3px solid var(--secondary-color); padding-bottom: var(--spacing-xs); margin-top: var(--spacing-xl); }
h3 { font-size: 1.5rem; color: var(--secondary-color); }
h4 { font-size: 1.2rem; }
p { margin: var(--spacing-sm) 0; }
sup a { color: var(--secondary-color); font-size: 0.8em; text-decoration: none; }
sup a:hover { text-decoration: underline; }
a { color: var(--primary-color); text-decoration: none; border-bottom: 1px solid transparent; transition: border-color 0.25s; }
a:hover { border-bottom-color: var(--primary-color); }

/* ===== Header ===== */
header { background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%); color: white; padding: var(--spacing-xl) 0; text-align: center; }
header h1 { color: white; margin-bottom: var(--spacing-xs); }
header .subtitle { font-size: 1.25rem; font-weight: 300; margin: var(--spacing-sm) 0; opacity: 0.95; }
header .byline { font-size: 0.95rem; font-style: italic; opacity: 0.85; margin-top: var(--spacing-xs); }

/* ===== Navigation ===== */
nav { background: var(--background-alt); border-bottom: 2px solid var(--border-color); position: sticky; top: 0; z-index: 100; box-shadow: var(--shadow); }
nav ul { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; justify-content: center; }
nav li { margin: 0; }
nav a { display: block; padding: var(--spacing-sm) var(--spacing-md); color: var(--text-color); font-weight: 500; font-size: 0.9rem; border-bottom: 3px solid transparent; transition: all 0.25s; border-bottom: none; }
nav a:hover { background: var(--background); color: var(--primary-color); border-bottom: 3px solid var(--accent-color); }

/* ===== Main ===== */
main { padding: var(--spacing-xl) 0; min-height: 60vh; }
.chapter { margin-bottom: var(--spacing-xl); }

/* ===== Pull Quotes ===== */
.pull-quote { font-family: var(--font-heading); font-size: 1.35rem; line-height: 1.55; color: var(--primary-color); padding: var(--spacing-md) var(--spacing-lg); margin: var(--spacing-lg) 0; border-left: 5px solid var(--accent-color); background: var(--background-alt); font-style: italic; border-radius: var(--border-radius); }

/* ===== Sidebars ===== */
.sidebar { background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%); color: white; padding: var(--spacing-md); border-radius: var(--border-radius); margin: var(--spacing-lg) 0; box-shadow: var(--shadow); }
.sidebar h4 { color: white; margin-top: 0; border-bottom: 2px solid rgba(255,255,255,0.3); padding-bottom: var(--spacing-xs); }
.sidebar p { margin: var(--spacing-xs) 0; font-size: 0.95rem; }
.sidebar ul { margin: var(--spacing-xs) 0; padding-left: var(--spacing-md); }
.sidebar li { margin: var(--spacing-xs) 0; }
.sidebar strong { color: var(--accent-color); }

/* ===== Key Insights ===== */
.key-insight { background: var(--background-alt); border: 2px solid var(--primary-color); border-radius: var(--border-radius); padding: var(--spacing-md); margin: var(--spacing-lg) 0; }
.key-insight h3, .key-insight h4 { margin-top: 0; color: var(--primary-color); }
.key-insight ul, .key-insight ol { margin: var(--spacing-xs) 0; padding-left: var(--spacing-lg); }
.key-insight li { margin: var(--spacing-xs) 0; }
.key-insight.warning { border-color: var(--accent-color); background: rgba(247,201,72,0.06); }
.key-insight.warning h3, .key-insight.warning h4 { color: #8a5c00; }

/* ===== Tip / Info Card ===== */
.tip-card { background: var(--background-alt); border: 2px solid var(--border-color); border-left: 5px solid var(--secondary-color); border-radius: var(--border-radius); padding: var(--spacing-md); margin: var(--spacing-md) 0; box-shadow: var(--shadow); }
.tip-card h4 { margin-top: 0; color: var(--primary-color); }

/* ===== Lists ===== */
ul, ol { padding-left: var(--spacing-lg); margin: var(--spacing-sm) 0; }
li { margin: var(--spacing-xs) 0; line-height: 1.65; }
li strong { color: var(--primary-color); }

/* ===== References ===== */
.references { counter-reset: ref-counter; list-style: none; padding-left: 0; }
.references li { counter-increment: ref-counter; position: relative; padding-left: var(--spacing-lg); margin: var(--spacing-sm) 0; font-size: 0.88rem; line-height: 1.6; }
.references li::before { content: "[" counter(ref-counter) "]"; position: absolute; left: 0; font-weight: bold; color: var(--primary-color); }
.references li em { color: var(--secondary-color); }

/* ===== Footer ===== */
footer { background: var(--background-alt); border-top: 2px solid var(--border-color); padding: var(--spacing-xl) 0; margin-top: var(--spacing-xl); }
footer .disclaimer { background: rgba(26,107,138,0.05); padding: var(--spacing-md); border-radius: var(--border-radius); border-left: 4px solid var(--accent-color); margin-bottom: var(--spacing-lg); font-size: 0.9rem; line-height: 1.6; }
footer .disclaimer strong { color: var(--primary-color); }
footer .copyright { text-align: center; color: var(--text-light); font-size: 0.9rem; }
footer .copyright p { margin: var(--spacing-xs) 0; }
footer .last-updated { font-size: 0.85rem; font-style: italic; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
    html { font-size: 15px; }
    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    h3 { font-size: 1.3rem; }
    nav ul { flex-direction: column; }
    nav a { padding: var(--spacing-sm); border-left: 3px solid transparent; border-bottom: 1px solid var(--border-color) !important; }
    nav a:hover { border-left-color: var(--accent-color); border-bottom-color: var(--border-color) !important; border-bottom: 1px solid var(--border-color) !important; }
    .pull-quote { font-size: 1.2rem; padding: var(--spacing-sm) var(--spacing-md); }
}

@media (max-width: 480px) {
    html { font-size: 14px; }
    header { padding: var(--spacing-lg) 0; }
    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.5rem; }
    .container { padding: 0 var(--spacing-sm); }
    .sidebar, .key-insight { padding: var(--spacing-sm); }
    .pull-quote { font-size: 1.1rem; }
    .tip-card { padding: var(--spacing-sm); }
}

/* ===== Print ===== */
@media print {
    * { background: white !important; color: black !important; box-shadow: none !important; }
    nav { display: none; }
    header { background: white !important; color: black !important; border-bottom: 3px solid black; }
    header h1, header .subtitle, header .byline { color: black !important; }
    a { text-decoration: underline; color: black !important; }
    .pull-quote, .sidebar, .key-insight, .tip-card { border: 2px solid black; page-break-inside: avoid; }
    h2, h3 { page-break-after: avoid; }
    .chapter { page-break-before: always; }
    .chapter:first-of-type { page-break-before: avoid; }
    footer { border-top: 2px solid black; }
}

/* ===== Accessibility ===== */
a:focus-visible, button:focus-visible { outline: 3px solid var(--accent-color); outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; } }
@media (prefers-contrast: high) { :root { --border-color: #000; } .pull-quote, .sidebar, .key-insight { border-width: 3px; } }

/* ===== Utility ===== */
.text-center { text-align: center; }
.text-light { color: var(--text-light); }
.mt-lg { margin-top: var(--spacing-lg); }
.mb-lg { margin-bottom: var(--spacing-lg); }