/* ================================================================
   BillError — Design System
   Fonts: Instrument Serif (display), DM Sans (body)
   License: Google Fonts (OFL/Apache 2.0) — commercial use OK
   ================================================================ */

/* ---- Reset ---- */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

/* ---- Accessibility: skip link ---- */
.skip-link {
    position: absolute;
    top: -100%;
    left: 16px;
    z-index: 9999;
    padding: 8px 16px;
    background: var(--ink);
    color: var(--surface);
    font-family: var(--font-body);
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    border-radius: 0 0 6px 6px;
    transition: top 0.15s ease;
}
.skip-link:focus {
    top: 0;
    outline: 2px solid var(--red-600);
    outline-offset: 2px;
}

:root {
    /* Palette */
    --red-600: #dc2626;
    --red-700: #b91c1c;
    --red-800: #991b1b;
    --red-50: #fef2f2;
    --red-100: #fee2e2;

    --ink: #0f0f0f;
    --ink-secondary: #4a4a4a;
    --ink-muted: #7a7a7a;
    --ink-faint: #a3a3a3;

    --surface: #ffffff;
    --surface-raised: #fafafa;
    --surface-sunken: #f5f5f4;
    --border: #e5e5e5;
    --border-light: #f0f0ef;

    --green-600: #16a34a;
    --green-50: #f0fdf4;
    --green-100: #dcfce7;
    --green-border: #bbf7d0;

    --blue-50: #eff6ff;
    --blue-100: #dbeafe;
    --blue-600: #2563eb;
    --blue-800: #1e3a8a;

    --amber-50: #fffbeb;
    --amber-100: #fef3c7;
    --amber-600: #d97706;
    --amber-border: #fde68a;

    --navy: #0c1220;
    --navy-light: #1a2332;

    /* Typography */
    --font-display: 'Instrument Serif', Georgia, serif;
    --font-body: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'DM Mono', 'SF Mono', 'Fira Code', monospace;

    /* Spacing scale */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;
    --space-4xl: 96px;

    /* Radius */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 20px;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 2px 8px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-lg: 0 4px 16px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.04);
    --shadow-xl: 0 8px 32px rgba(0,0,0,0.1), 0 2px 8px rgba(0,0,0,0.04);

    /* Transitions */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --duration-fast: 150ms;
    --duration-normal: 250ms;
    --duration-slow: 400ms;
}

/* ---- Dark mode overrides ---- */
[data-theme="dark"] {
    --ink: #e8e8e8;
    --ink-secondary: #b0b0b0;
    --ink-muted: #888;
    --ink-faint: #666;

    --surface: #121212;
    --surface-raised: #1a1a1a;
    --surface-sunken: #0e0e0e;
    --border: #2a2a2a;
    --border-light: #222;

    --red-50: #2a1515;
    --red-100: #3a1c1c;
    --green-50: #152a18;
    --green-100: #1c3a20;
    --green-border: #1c5a2c;
    --blue-50: #151c2a;
    --blue-100: #1c243a;
    --amber-50: #2a2415;
    --amber-100: #3a301c;
    --amber-border: #5a4a1c;

    --navy: #080c14;
    --navy-light: #0f1520;

    --shadow-sm: 0 1px 2px rgba(0,0,0,0.2);
    --shadow-md: 0 2px 8px rgba(0,0,0,0.3), 0 1px 2px rgba(0,0,0,0.2);
    --shadow-lg: 0 4px 16px rgba(0,0,0,0.35), 0 2px 4px rgba(0,0,0,0.2);
    --shadow-xl: 0 8px 32px rgba(0,0,0,0.4), 0 2px 8px rgba(0,0,0,0.2);

    color-scheme: dark;
}

body {
    font-family: var(--font-body);
    background: var(--surface);
    color: var(--ink);
    line-height: 1.6;
    font-size: 15px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
}

/* ---- Navigation ---- */
nav {
    padding: 0 40px;
    height: 64px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--navy);
    position: sticky;
    top: 0;
    z-index: 100;
}
.logo {
    font-family: var(--font-display);
    font-size: 26px;
    font-weight: 400;
    color: #fff;
    letter-spacing: -0.02em;
}
.logo span { color: var(--red-600); }
.logo a {
    text-decoration: none;
    color: inherit;
    display: flex;
    align-items: center;
    gap: 2px;
}
.nav-link {
    font-size: 14px;
    font-weight: 500;
    color: rgba(255,255,255,0.7);
    text-decoration: none;
    padding: 6px 14px;
    border-radius: var(--radius-sm);
    transition: color var(--duration-fast), background var(--duration-fast);
}
.nav-link:hover {
    color: #fff;
    background: rgba(255,255,255,0.08);
}

/* ---- Container ---- */
.container {
    max-width: 780px;
    margin: var(--space-2xl) auto;
    padding: 0 var(--space-lg);
}

/* ---- Typography ---- */
h1 {
    font-family: var(--font-display);
    font-size: 36px;
    font-weight: 400;
    line-height: 1.2;
    letter-spacing: -0.02em;
    margin-bottom: var(--space-md);
}
h2 {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 400;
    line-height: 1.3;
    letter-spacing: -0.01em;
    margin-top: var(--space-xl);
    margin-bottom: var(--space-md);
}
h3 {
    font-family: var(--font-body);
    font-size: 16px;
    font-weight: 600;
    margin-top: var(--space-lg);
    margin-bottom: var(--space-sm);
}

/* ---- Links ---- */
a { color: var(--red-600); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---- Buttons ---- */
.btn-primary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    background: var(--red-600);
    color: #fff;
    border: none;
    border-radius: var(--radius-md);
    padding: 14px 28px;
    font-family: var(--font-body);
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--duration-fast), transform var(--duration-fast), box-shadow var(--duration-fast);
    box-shadow: 0 1px 3px rgba(220,38,38,0.2);
}
.btn-primary:hover {
    background: var(--red-700);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(220,38,38,0.25);
    text-decoration: none;
}
.btn-primary:active { transform: translateY(0); }
.btn-primary:disabled {
    background: var(--border);
    color: var(--ink-muted);
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

/* Alias for old class */
.btn-red { composes: btn-primary; }

.btn-secondary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    background: var(--surface);
    color: var(--ink);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 12px 24px;
    font-family: var(--font-body);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--duration-fast), border-color var(--duration-fast);
}
.btn-secondary:hover {
    background: var(--surface-sunken);
    border-color: var(--ink-faint);
    text-decoration: none;
}

/* ---- Form inputs ---- */
.form-group { margin-bottom: var(--space-md); }
.form-group label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: var(--ink-secondary);
    margin-bottom: 6px;
    letter-spacing: 0.01em;
}
.form-group input {
    width: 100%;
    padding: 11px 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-family: var(--font-body);
    font-size: 15px;
    outline: none;
    transition: border-color var(--duration-fast), box-shadow var(--duration-fast);
    background: var(--surface);
}
.form-group input:focus {
    border-color: var(--red-600);
    box-shadow: 0 0 0 3px rgba(220,38,38,0.08);
}
.form-group input::placeholder { color: var(--ink-faint); }

/* ---- Cards ---- */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    box-shadow: var(--shadow-sm);
}
.card-elevated {
    background: var(--surface);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    box-shadow: var(--shadow-md);
}

/* ---- Badge ---- */
.badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 3px 10px;
    border-radius: 100px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.02em;
    text-transform: uppercase;
}
.badge-red { background: var(--red-50); color: var(--red-700); border: 1px solid var(--red-100); }
.badge-green { background: var(--green-50); color: var(--green-600); border: 1px solid var(--green-100); }
.badge-blue { background: var(--blue-50); color: var(--blue-600); border: 1px solid var(--blue-100); }
.badge-amber { background: var(--amber-50); color: var(--amber-600); border: 1px solid var(--amber-100); }

/* ---- Tables ---- */
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th {
    text-align: left;
    padding: 10px 14px;
    background: var(--surface-sunken);
    border-bottom: 1px solid var(--border);
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--ink-muted);
}
td {
    text-align: left;
    padding: 10px 14px;
    border-bottom: 1px solid var(--border-light);
    color: var(--ink-secondary);
}

/* ---- Footer ---- */
footer {
    padding: 0;
    color: var(--ink-faint);
    font-size: 13px;
    border-top: 1px solid var(--border-light);
    background: var(--surface-sunken);
    line-height: 1.8;
}
footer a {
    color: var(--ink-muted);
    transition: color var(--duration-fast);
}
footer a:hover { color: var(--ink); text-decoration: underline; }
.footer-inner {
    max-width: 920px;
    margin: 0 auto;
    padding: var(--space-2xl) var(--space-xl) var(--space-lg);
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: var(--space-xl);
}
.footer-brand p {
    color: var(--ink-muted);
    font-size: 13px;
    max-width: 280px;
    line-height: 1.5;
}
.footer-social {
    display: flex;
    gap: 12px;
    margin-top: 12px;
}
.footer-social a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: var(--radius-md);
    color: var(--ink-muted);
    background: var(--surface);
    border: 1px solid var(--border);
    transition: color var(--duration-fast), border-color var(--duration-fast), background var(--duration-fast);
}
.footer-social a:hover {
    color: var(--ink);
    border-color: var(--ink-muted);
    background: var(--surface-raised);
    text-decoration: none;
}
.footer-col {
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.footer-col strong {
    font-size: 12px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--ink-secondary);
    margin-bottom: 4px;
}
.footer-col a {
    font-size: 13px;
    color: var(--ink-muted);
    text-decoration: none;
}
.footer-col a:hover { color: var(--ink); }
.footer-bottom {
    text-align: center;
    padding: var(--space-lg) var(--space-xl);
    border-top: 1px solid var(--border-light);
}
.disclaimer { margin-top: 4px; font-size: 12px; }
.footer-links { margin-top: var(--space-sm); }

/* ---- Theme toggle ---- */
.theme-toggle {
    background: none;
    border: 1px solid rgba(255,255,255,0.15);
    border-radius: var(--radius-sm);
    color: rgba(255,255,255,0.7);
    cursor: pointer;
    padding: 6px 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--duration-fast), background var(--duration-fast), border-color var(--duration-fast);
    line-height: 1;
}
.theme-toggle:hover {
    color: #fff;
    background: rgba(255,255,255,0.08);
    border-color: rgba(255,255,255,0.25);
}
.theme-toggle svg { width: 18px; height: 18px; }
.theme-toggle .icon-moon { display: block; }
.theme-toggle .icon-sun { display: none; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }

/* Dark mode form/input adjustments */
[data-theme="dark"] .form-group input {
    background: var(--surface-raised);
    color: var(--ink);
}
[data-theme="dark"] img { opacity: 0.92; }

/* ---- Spinner ---- */
.spinner {
    border: 3px solid var(--border);
    border-top-color: var(--red-600);
    border-radius: 50%;
    animation: spin 0.7s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ---- Legal pages ---- */
.legal-body { line-height: 1.8; }
.legal-body .container { max-width: 720px; margin-bottom: 80px; }
.legal-body p { margin-bottom: var(--space-md); font-size: 15px; color: var(--ink-secondary); }
.legal-body ul { margin-bottom: var(--space-md); padding-left: var(--space-lg); }
.legal-body li { margin-bottom: var(--space-sm); font-size: 15px; color: var(--ink-secondary); }
.updated { color: var(--ink-muted); font-size: 14px; margin-bottom: var(--space-xl); }

/* ---- Notice boxes ---- */
.notice {
    border-radius: var(--radius-md);
    padding: var(--space-md) var(--space-lg);
    margin-bottom: var(--space-lg);
    font-size: 14px;
    line-height: 1.6;
}
.notice-info { background: var(--blue-50); border: 1px solid var(--blue-100); color: var(--blue-800); }
.notice-success { background: var(--green-50); border: 1px solid var(--green-border); color: #166534; }
.notice-warning { background: var(--amber-50); border: 1px solid var(--amber-border); color: #92400e; }
.notice-error { background: var(--red-50); border: 1px solid var(--red-100); color: var(--red-800); }

/* ---- Animations ---- */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}
@keyframes slideDown {
    from { opacity: 0; transform: translateY(-12px); }
    to { opacity: 1; transform: translateY(0); }
}
.animate-in {
    animation: fadeInUp var(--duration-slow) var(--ease-out) both;
}
.animate-in-delay-1 { animation-delay: 80ms; }
.animate-in-delay-2 { animation-delay: 160ms; }
.animate-in-delay-3 { animation-delay: 240ms; }
.animate-in-delay-4 { animation-delay: 320ms; }

/* ---- Scroll-triggered reveal ---- */
.reveal {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
}
.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}
/* Staggered children inside a revealed parent */
.reveal-children > * {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.5s var(--ease-out), transform 0.5s var(--ease-out);
}
.reveal-children.visible > * {
    opacity: 1;
    transform: translateY(0);
}
.reveal-children.visible > *:nth-child(1) { transition-delay: 0ms; }
.reveal-children.visible > *:nth-child(2) { transition-delay: 80ms; }
.reveal-children.visible > *:nth-child(3) { transition-delay: 160ms; }
.reveal-children.visible > *:nth-child(4) { transition-delay: 240ms; }
.reveal-children.visible > *:nth-child(5) { transition-delay: 320ms; }
.reveal-children.visible > *:nth-child(6) { transition-delay: 400ms; }
/* Respect prefers-reduced-motion */
@media (prefers-reduced-motion: reduce) {
    .reveal, .reveal-children > * {
        opacity: 1;
        transform: none;
        transition: none;
    }
}

/* ---- Responsive ---- */
@media (max-width: 768px) {
    nav { padding: 0 20px; height: 56px; }
    .logo { font-size: 22px; }
    .container { padding: 0 20px; margin: var(--space-xl) auto; }
    h1 { font-size: 28px; }
    h2 { font-size: 22px; }
    .footer-inner { grid-template-columns: 1fr 1fr 1fr; gap: var(--space-lg); }
    .footer-brand { grid-column: 1 / -1; }
}

@media (max-width: 640px) {
    nav { padding: 0 16px; height: 52px; }
    .logo { font-size: 20px; }
    .container { padding: 0 16px; margin: var(--space-lg) auto; }
    h1 { font-size: 24px; }
    .footer-inner { grid-template-columns: 1fr; padding: var(--space-xl) var(--space-md) var(--space-md); gap: var(--space-md); }
    .footer-bottom { padding: var(--space-md); }
}

/* ---- Referral CTA boxes ---- */
.referral-box {
    background: var(--surface);
    border: 1.5px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    margin: var(--space-2xl) 0;
}
.referral-header {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
    font-weight: 700;
    color: var(--ink);
    margin-bottom: var(--space-md);
    text-transform: uppercase;
    letter-spacing: 0.04em;
}
.referral-icon { width: 20px; height: 20px; color: var(--red-600); }
.referral-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-lg);
    padding: var(--space-md) 0;
    border-top: 1px solid var(--border-light);
}
.referral-item:last-of-type { border-bottom: 1px solid var(--border-light); }
.referral-info { flex: 1; }
.referral-info strong {
    display: block;
    font-size: 15px;
    color: var(--ink);
    margin-bottom: 2px;
}
.referral-info p {
    font-size: 13px;
    color: var(--ink-secondary);
    line-height: 1.5;
    margin: 0;
}
.referral-note {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    color: var(--green-600);
    margin-top: 4px;
}
.referral-btn {
    flex-shrink: 0;
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 10px 20px;
    background: var(--red-600);
    color: #fff;
    font-size: 13px;
    font-weight: 600;
    border-radius: var(--radius-md);
    text-decoration: none;
    white-space: nowrap;
    transition: background var(--duration-fast), transform var(--duration-fast);
}
.referral-btn:hover { background: var(--red-700); transform: translateY(-1px); color: #fff; text-decoration: none; }
.referral-disclosure {
    font-size: 11px;
    color: var(--ink-faint);
    margin: var(--space-sm) 0 0;
    font-style: italic;
}

/* ---- Ad slots ---- */
.ad-slot {
    margin: var(--space-xl) 0;
    text-align: center;
    min-height: 90px;
}

@media (max-width: 640px) {
    .referral-item { flex-direction: column; align-items: flex-start; gap: var(--space-sm); }
    .referral-btn { width: 100%; justify-content: center; }
}