/* =============================================
   DiscriminantCalculator.com — Global Styles
   ============================================= */

@import url('https://fonts.googleapis.com/css2?family=DM+Serif+Display:ital@0;1&family=DM+Sans:wght@300;400;500;600&family=JetBrains+Mono:wght@400;600&display=swap');

/* --- CSS Variables --- */
:root {
  --blue: #1a6bff;
  --blue-dark: #0f4fcf;
  --blue-light: #e8f0ff;
  --ink: #111827;
  --ink-soft: #374151;
  --muted: #6b7280;
  --border: #e5e7eb;
  --bg: #ffffff;
  --bg-soft: #f9fafb;
  --bg-section: #f3f6ff;
  --card-shadow: 0 2px 12px rgba(26,107,255,0.08), 0 1px 3px rgba(0,0,0,0.06);
  --card-hover: 0 8px 32px rgba(26,107,255,0.14), 0 2px 8px rgba(0,0,0,0.08);
  --radius: 14px;
  --radius-sm: 8px;
  --font-display: 'DM Serif Display', Georgia, serif;
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --transition: 0.22s cubic-bezier(0.4, 0, 0.2, 1);
  --max-w: 1100px;
}

/* --- Reset --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body { font-family: var(--font-body); color: var(--ink); background: var(--bg); line-height: 1.6; -webkit-font-smoothing: antialiased; }
img { max-width: 100%; height: auto; display: block; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
ul { list-style: none; }

/* --- Layout --- */
.container { max-width: var(--max-w); margin: 0 auto; padding: 0 20px; }
.section { padding: 72px 0; }
.section--soft { background: var(--bg-soft); }
.section--blue { background: var(--bg-section); }

/* --- Typography --- */
h1, h2, h3, h4 { font-family: var(--font-display); line-height: 1.2; color: var(--ink); }
h1 { font-size: clamp(2rem, 5vw, 3rem); }
h2 { font-size: clamp(1.6rem, 3.5vw, 2.2rem); }
h3 { font-size: 1.25rem; }
p { color: var(--ink-soft); }
.text-muted { color: var(--muted); font-size: 0.9rem; }
.section-header { text-align: center; margin-bottom: 48px; }
.section-header p { max-width: 560px; margin: 12px auto 0; }

/* --- Buttons --- */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 12px 26px; border-radius: 50px; font-family: var(--font-body);
  font-weight: 600; font-size: 0.95rem; cursor: pointer;
  border: none; transition: var(--transition); text-decoration: none;
}
.btn-primary { background: var(--blue); color: #fff; }
.btn-primary:hover { background: var(--blue-dark); transform: translateY(-1px); box-shadow: 0 4px 18px rgba(26,107,255,0.35); text-decoration: none; color: #fff; }
.btn-outline { background: transparent; color: var(--blue); border: 2px solid var(--blue); }
.btn-outline:hover { background: var(--blue); color: #fff; text-decoration: none; }
.btn-lg { padding: 16px 36px; font-size: 1.05rem; }

/* =============================================
   HEADER / NAV
   ============================================= */
.site-header {
  position: sticky; top: 0; z-index: 1000;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: box-shadow var(--transition);
}
.site-header.scrolled { box-shadow: 0 2px 20px rgba(0,0,0,0.08); }

.nav-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 64px;
}
.nav-logo {
  font-family: var(--font-display); font-size: 1.3rem; color: var(--ink);
  display: flex; align-items: center; gap: 8px;
}
.nav-logo span { color: var(--blue); }
.logo-icon {
  width: 34px; height: 34px; background: var(--blue); border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  color: white; font-family: var(--font-mono); font-size: 0.7rem; font-weight: 600; line-height: 1.1; text-align: center;
}
.nav-menu { display: flex; align-items: center; gap: 4px; }
.nav-menu a {
  padding: 8px 16px; border-radius: 8px; font-weight: 500;
  color: var(--ink-soft); transition: var(--transition); font-size: 0.95rem;
}
.nav-menu a:hover, .nav-menu a.active { color: var(--blue); background: var(--blue-light); text-decoration: none; }
.nav-hamburger { display: none; background: none; border: none; cursor: pointer; padding: 8px; border-radius: 8px; }
.nav-hamburger span { display: block; width: 22px; height: 2px; background: var(--ink); border-radius: 2px; transition: var(--transition); margin: 5px 0; }

/* =============================================
   HERO
   ============================================= */
.hero {
  padding: 72px 0 56px;
  background: linear-gradient(135deg, #f0f5ff 0%, #ffffff 60%);
  position: relative; overflow: hidden;
}
.hero::before {
  content: 'D=b²-4ac';
  position: absolute; right: -20px; top: 50%; transform: translateY(-50%);
  font-family: var(--font-display); font-size: 9rem; color: rgba(26,107,255,0.04);
  white-space: nowrap; pointer-events: none; user-select: none;
  font-style: italic;
}
.hero-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 56px; align-items: start; }
.hero-text .badge {
  display: inline-flex; align-items: center; gap: 6px;
  background: var(--blue-light); color: var(--blue);
  padding: 6px 14px; border-radius: 50px; font-size: 0.82rem; font-weight: 600;
  margin-bottom: 20px; letter-spacing: 0.02em;
}
.hero-text h1 { margin-bottom: 16px; }
.hero-text p { font-size: 1.05rem; max-width: 480px; margin-bottom: 28px; }
.hero-formula {
  font-family: var(--font-mono); font-size: 1.1rem;
  background: var(--blue-light); color: var(--blue);
  display: inline-block; padding: 10px 20px; border-radius: 10px;
  font-weight: 600; margin-bottom: 28px; border-left: 4px solid var(--blue);
}
.hero-stats { display: flex; gap: 28px; margin-top: 24px; }
.stat-item { text-align: left; }
.stat-num { font-family: var(--font-display); font-size: 1.7rem; color: var(--blue); font-weight: 700; }
.stat-label { font-size: 0.8rem; color: var(--muted); }

/* =============================================
   CALCULATOR CARD
   ============================================= */
.calc-card {
  background: #fff; border-radius: var(--radius); padding: 36px;
  box-shadow: var(--card-shadow); border: 1px solid var(--border);
  position: relative;
}
.calc-card::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 4px;
  background: linear-gradient(90deg, var(--blue), #6b5bff);
  border-radius: var(--radius) var(--radius) 0 0;
}
.calc-title { font-family: var(--font-display); font-size: 1.3rem; margin-bottom: 6px; }
.calc-subtitle { color: var(--muted); font-size: 0.88rem; margin-bottom: 24px; }

.input-row { display: flex; gap: 12px; margin-bottom: 20px; }
.input-group { flex: 1; }
.input-group label { display: block; font-size: 0.82rem; font-weight: 600; color: var(--ink); margin-bottom: 6px; letter-spacing: 0.03em; }
.input-group .label-sub { font-size: 0.75rem; color: var(--muted); font-weight: 400; margin-left: 4px; }
.input-group input {
  width: 100%; padding: 13px 14px; border: 2px solid var(--border);
  border-radius: var(--radius-sm); font-family: var(--font-mono); font-size: 1rem;
  color: var(--ink); background: var(--bg-soft); transition: var(--transition);
  outline: none; text-align: center;
}
.input-group input:focus { border-color: var(--blue); background: #fff; box-shadow: 0 0 0 3px rgba(26,107,255,0.12); }
.input-group input.error { border-color: #ef4444; background: #fff5f5; }

.calc-actions { display: flex; gap: 10px; margin-bottom: 24px; }
.calc-actions .btn { flex: 1; justify-content: center; border-radius: var(--radius-sm); }
.btn-reset { background: var(--bg-soft); color: var(--ink-soft); border: 1px solid var(--border); }
.btn-reset:hover { background: var(--border); text-decoration: none; color: var(--ink); }

/* --- Result Box --- */
.result-box { display: none; }
.result-box.show { display: block; animation: fadeSlide 0.4s ease; }
@keyframes fadeSlide { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

.result-value {
  background: linear-gradient(135deg, var(--blue) 0%, #3b82f6 100%);
  border-radius: var(--radius-sm); padding: 20px 24px;
  color: #fff; text-align: center; margin-bottom: 14px;
}
.result-value .d-label { font-size: 0.82rem; opacity: 0.85; margin-bottom: 4px; font-weight: 500; }
.result-value .d-num { font-family: var(--font-display); font-size: 2.4rem; font-weight: 700; }

.nature-badge {
  text-align: center; padding: 10px 16px; border-radius: var(--radius-sm);
  font-weight: 600; font-size: 0.95rem; margin-bottom: 16px;
}
.nature-two { background: #d1fae5; color: #065f46; }
.nature-one { background: #fef3c7; color: #78350f; }
.nature-complex { background: #fce7f3; color: #831843; }

.steps-box {
  background: var(--bg-soft); border-radius: var(--radius-sm);
  padding: 18px 20px; border: 1px solid var(--border);
}
.steps-box h4 { font-size: 0.88rem; font-weight: 600; color: var(--muted); letter-spacing: 0.05em; text-transform: uppercase; margin-bottom: 12px; }
.step-line {
  font-family: var(--font-mono); font-size: 0.88rem; color: var(--ink-soft);
  padding: 5px 0; border-bottom: 1px dashed var(--border);
}
.step-line:last-child { border-bottom: none; color: var(--blue); font-weight: 600; }

.error-msg {
  background: #fff5f5; color: #dc2626; border: 1px solid #fecaca;
  border-radius: var(--radius-sm); padding: 12px 16px;
  font-size: 0.9rem; display: none;
}
.error-msg.show { display: block; animation: fadeSlide 0.3s ease; }

/* =============================================
   TOOL CARDS
   ============================================= */
.tools-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 20px; }
.tool-card {
  background: #fff; border-radius: var(--radius); padding: 28px 24px;
  border: 1px solid var(--border); transition: var(--transition);
  box-shadow: var(--card-shadow); display: flex; flex-direction: column;
}
.tool-card:hover { box-shadow: var(--card-hover); transform: translateY(-3px); border-color: rgba(26,107,255,0.2); }
.tool-icon {
  width: 44px; height: 44px; background: var(--blue-light); border-radius: 10px;
  display: flex; align-items: center; justify-content: center; margin-bottom: 14px;
  font-size: 1.3rem;
}
.tool-card h3 { font-size: 1rem; margin-bottom: 8px; }
.tool-card p { font-size: 0.875rem; color: var(--muted); flex: 1; margin-bottom: 16px; }
.tool-card .btn { font-size: 0.85rem; padding: 9px 18px; align-self: flex-start; }

/* =============================================
   BLOG CARDS
   ============================================= */
.blog-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }
.blog-card {
  background: #fff; border-radius: var(--radius); overflow: hidden;
  border: 1px solid var(--border); box-shadow: var(--card-shadow);
  transition: var(--transition); display: flex; flex-direction: column;
}
.blog-card:hover { box-shadow: var(--card-hover); transform: translateY(-3px); }
.blog-card-thumb {
  height: 160px; background: linear-gradient(135deg, var(--blue-light), #dbeafe);
  display: flex; align-items: center; justify-content: center;
  font-size: 2.8rem; position: relative; overflow: hidden;
}
.blog-card-thumb::after {
  content: attr(data-formula); position: absolute; bottom: 8px; right: 14px;
  font-family: var(--font-mono); font-size: 0.75rem; color: rgba(26,107,255,0.5); font-weight: 600;
}
.blog-card-body { padding: 22px; flex: 1; display: flex; flex-direction: column; }
.blog-tag {
  display: inline-block; background: var(--blue-light); color: var(--blue);
  font-size: 0.75rem; font-weight: 600; padding: 3px 10px; border-radius: 50px;
  margin-bottom: 10px; letter-spacing: 0.03em;
}
.blog-card h3 { font-size: 1.05rem; margin-bottom: 8px; }
.blog-card p { font-size: 0.875rem; color: var(--muted); flex: 1; margin-bottom: 16px; }
.blog-card .btn { font-size: 0.82rem; padding: 8px 16px; align-self: flex-start; }

/* =============================================
   HOW IT WORKS
   ============================================= */
.how-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 24px; }
.how-step {
  text-align: center; padding: 28px 20px;
  background: #fff; border-radius: var(--radius); border: 1px solid var(--border);
}
.step-num {
  width: 48px; height: 48px; border-radius: 50%; background: var(--blue);
  color: #fff; font-family: var(--font-display); font-size: 1.4rem;
  display: flex; align-items: center; justify-content: center; margin: 0 auto 14px;
}
.how-step h3 { font-size: 1rem; margin-bottom: 8px; }
.how-step p { font-size: 0.875rem; }

/* =============================================
   FAQ
   ============================================= */
.faq-list { max-width: 740px; margin: 0 auto; }
.faq-item { border: 1px solid var(--border); border-radius: var(--radius-sm); margin-bottom: 12px; overflow: hidden; }
.faq-q {
  width: 100%; padding: 18px 20px; background: #fff; border: none; cursor: pointer;
  display: flex; justify-content: space-between; align-items: center;
  font-family: var(--font-body); font-size: 0.95rem; font-weight: 600; color: var(--ink);
  text-align: left; transition: var(--transition);
}
.faq-q:hover { background: var(--bg-soft); }
.faq-q.open { background: var(--blue-light); color: var(--blue); }
.faq-icon { font-size: 1.2rem; transition: var(--transition); flex-shrink: 0; }
.faq-q.open .faq-icon { transform: rotate(45deg); }
.faq-a { padding: 0 20px; max-height: 0; overflow: hidden; transition: max-height 0.35s ease, padding 0.2s; }
.faq-a.open { max-height: 300px; padding: 16px 20px; }
.faq-a p { font-size: 0.9rem; color: var(--ink-soft); }

/* =============================================
   PAGE HERO (inner pages)
   ============================================= */
.page-hero {
  background: linear-gradient(135deg, #f0f5ff 0%, #ffffff 100%);
  padding: 56px 0 48px; text-align: center; border-bottom: 1px solid var(--border);
}
.page-hero h1 { margin-bottom: 12px; }
.page-hero p { max-width: 560px; margin: 0 auto; font-size: 1.05rem; }
.breadcrumb { display: flex; align-items: center; gap: 8px; justify-content: center; margin-bottom: 20px; font-size: 0.85rem; }
.breadcrumb a { color: var(--blue); }
.breadcrumb span { color: var(--muted); }

/* =============================================
   CONTACT FORM
   ============================================= */
.contact-grid { display: grid; grid-template-columns: 1fr 1.6fr; gap: 48px; align-items: start; }
.contact-info h3 { margin-bottom: 16px; }
.contact-info p { margin-bottom: 20px; }
.contact-fact { display: flex; align-items: flex-start; gap: 14px; margin-bottom: 16px; }
.contact-fact-icon { width: 38px; height: 38px; background: var(--blue-light); border-radius: 8px; display: flex; align-items: center; justify-content: center; font-size: 1.1rem; flex-shrink: 0; }
.contact-fact-body strong { display: block; font-size: 0.88rem; }
.contact-fact-body span { font-size: 0.85rem; color: var(--muted); }

.form-group { margin-bottom: 18px; }
.form-group label { display: block; font-weight: 600; font-size: 0.88rem; margin-bottom: 6px; }
.form-group input, .form-group textarea, .form-group select {
  width: 100%; padding: 13px 15px; border: 2px solid var(--border);
  border-radius: var(--radius-sm); font-family: var(--font-body); font-size: 0.95rem;
  color: var(--ink); background: var(--bg-soft); transition: var(--transition); outline: none;
}
.form-group input:focus, .form-group textarea:focus { border-color: var(--blue); background: #fff; box-shadow: 0 0 0 3px rgba(26,107,255,0.1); }
.form-group input.err, .form-group textarea.err { border-color: #ef4444; }
.form-group textarea { resize: vertical; min-height: 140px; }
.form-msg { padding: 12px 16px; border-radius: var(--radius-sm); margin-bottom: 16px; display: none; font-size: 0.9rem; }
.form-msg.success { background: #d1fae5; color: #065f46; display: block; }
.form-msg.error { background: #fee2e2; color: #991b1b; display: block; }
.field-err { font-size: 0.8rem; color: #dc2626; margin-top: 4px; display: none; }
.field-err.show { display: block; }

/* =============================================
   ABOUT PAGE
   ============================================= */
.about-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: center; }
.about-visual {
  background: linear-gradient(135deg, var(--blue-light), #dbeafe);
  border-radius: var(--radius); padding: 48px; text-align: center;
}
.about-visual .big-formula {
  font-family: var(--font-display); font-size: 2.4rem; color: var(--blue); font-style: italic;
  margin-bottom: 12px;
}
.about-visual p { font-size: 0.9rem; color: var(--muted); }
.feature-list { margin-top: 24px; }
.feature-item { display: flex; gap: 12px; align-items: flex-start; margin-bottom: 16px; }
.feature-check { color: var(--blue); font-size: 1.2rem; flex-shrink: 0; margin-top: 2px; }
.feature-item strong { display: block; font-size: 0.95rem; }
.feature-item p { font-size: 0.875rem; margin-top: 2px; }

/* =============================================
   PROSE (Privacy / Terms)
   ============================================= */
.prose-wrap { max-width: 780px; margin: 0 auto; }
.prose h2 { font-size: 1.5rem; margin: 40px 0 14px; padding-top: 20px; border-top: 1px solid var(--border); }
.prose h2:first-of-type { border-top: none; margin-top: 0; padding-top: 0; }
.prose h3 { font-size: 1.1rem; margin: 24px 0 10px; }
.prose p { margin-bottom: 14px; font-size: 0.95rem; color: var(--ink-soft); }
.prose ul { margin: 14px 0 14px 20px; }
.prose ul li { font-size: 0.95rem; color: var(--ink-soft); margin-bottom: 8px; list-style: disc; }
.prose a { color: var(--blue); }
.last-updated { display: inline-block; background: var(--bg-soft); border: 1px solid var(--border); border-radius: 6px; padding: 6px 14px; font-size: 0.82rem; color: var(--muted); margin-bottom: 32px; }

/* =============================================
   FOOTER
   ============================================= */
.site-footer {
  background: var(--ink); color: rgba(255,255,255,0.75);
  padding: 64px 0 32px;
}
.footer-grid { display: grid; grid-template-columns: 1.6fr 1fr 1fr 1fr; gap: 40px; margin-bottom: 48px; }
.footer-brand .nav-logo { color: #fff; margin-bottom: 14px; }
.footer-brand .nav-logo span { color: #6ba3ff; }
.footer-brand p { font-size: 0.88rem; color: rgba(255,255,255,0.6); line-height: 1.7; }
.footer-col h4 { color: #fff; font-family: var(--font-body); font-size: 0.82rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 16px; }
.footer-col ul li { margin-bottom: 10px; }
.footer-col ul li a { color: rgba(255,255,255,0.6); font-size: 0.9rem; transition: color var(--transition); }
.footer-col ul li a:hover { color: #fff; text-decoration: none; }
.footer-bottom { border-top: 1px solid rgba(255,255,255,0.1); padding-top: 28px; display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 12px; }
.footer-bottom p { font-size: 0.85rem; }
.footer-bottom-links { display: flex; gap: 20px; }
.footer-bottom-links a { font-size: 0.85rem; color: rgba(255,255,255,0.5); }
.footer-bottom-links a:hover { color: #fff; text-decoration: none; }

/* =============================================
   MOBILE RESPONSIVE
   ============================================= */
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; gap: 36px; }
  .hero::before { display: none; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .about-grid { grid-template-columns: 1fr; }
  .contact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 640px) {
  .section { padding: 48px 0; }
  .nav-menu { display: none; position: absolute; top: 64px; left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--border); flex-direction: column; padding: 12px 16px; gap: 4px; box-shadow: 0 4px 20px rgba(0,0,0,0.08); }
  .nav-menu.open { display: flex; }
  .nav-hamburger { display: block; }
  .input-row { flex-direction: column; }
  .hero-stats { gap: 16px; }
  .footer-grid { grid-template-columns: 1fr; }
  .tools-grid { grid-template-columns: 1fr; }
  .blog-grid { grid-template-columns: 1fr; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
}

/* =============================================
   UTILITIES
   ============================================= */
.text-center { text-align: center; }
.mt-8 { margin-top: 8px; }
.mt-12 { margin-top: 12px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mb-0 { margin-bottom: 0 !important; }
.highlight { color: var(--blue); }

/* Scroll animations */
.reveal { opacity: 0; transform: translateY(20px); transition: opacity 0.6s ease, transform 0.6s ease; }
.reveal.visible { opacity: 1; transform: translateY(0); }