@import url('https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;0,9..40,700;1,9..40,400&family=DM+Mono:wght@400;500&display=swap');

/* ── Reset & Variables ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --navy:      #0f172a;
  --navy-800:  #1e293b;
  --navy-700:  #334155;
  --navy-600:  #475569;
  --blue:      #3b82f6;
  --blue-dark: #2563eb;
  --blue-light:#eff6ff;
  --green:     #10b981;
  --red:       #ef4444;
  --white:     #ffffff;
  --gray-50:   #f8fafc;
  --gray-100:  #f1f5f9;
  --gray-200:  #e2e8f0;
  --gray-300:  #cbd5e1;
  --text:      #0f172a;
  --text-muted:#64748b;
  --radius:    12px;
  --radius-sm: 8px;
  --shadow:    0 4px 24px rgba(15,23,42,.08);
  --shadow-lg: 0 8px 48px rgba(15,23,42,.14);
  --transition:0.2s ease;
  --max-w:     1200px;
  --font:      'DM Sans', sans-serif;
  --mono:      'DM Mono', monospace;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--text);
  background: var(--white);
  -webkit-font-smoothing: antialiased;
}

/* ── Typography ── */
h1,h2,h3,h4,h5,h6 {
  font-weight: 700;
  line-height: 1.25;
  color: var(--navy);
  letter-spacing: -0.02em;
}
h1 { font-size: clamp(2rem, 5vw, 3.25rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2.25rem); }
h3 { font-size: clamp(1.15rem, 2.5vw, 1.5rem); }
h4 { font-size: 1.1rem; }
p  { color: var(--text-muted); }
a  { color: var(--blue); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--blue-dark); }
code, .mono { font-family: var(--mono); }
strong { color: var(--navy); font-weight: 600; }

/* ── Layout ── */
.container { max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem; }
section { padding: 5rem 0; }

/* ── Header ── */
header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(15,23,42,.97);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.header-inner {
  max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem;
  display: flex; align-items: center; justify-content: space-between;
  height: 64px;
}
.logo {
  display: flex; align-items: center; gap: .6rem;
  color: var(--white) !important; font-weight: 700; font-size: 1.1rem;
  letter-spacing: -0.02em;
}
.logo-icon {
  width: 34px; height: 34px; background: var(--blue);
  border-radius: 8px; display: grid; place-items: center;
  font-family: var(--mono); font-size: .75rem; color: white; font-weight: 500;
}
nav { display: flex; align-items: center; gap: 2rem; }
nav a { color: rgba(255,255,255,.75); font-size: .95rem; font-weight: 500; transition: color var(--transition); }
nav a:hover { color: var(--white); }
nav a.active { color: var(--white); }
.nav-cta {
  background: var(--blue); color: var(--white) !important;
  padding: .45rem 1.1rem; border-radius: 8px; font-size: .9rem !important;
}
.nav-cta:hover { background: var(--blue-dark) !important; color: white !important; }

/* ── Hero ── */
.hero {
  background: linear-gradient(135deg, var(--navy) 0%, #1a2744 60%, #0d1f3c 100%);
  padding: 6rem 0 5rem; position: relative; overflow: hidden;
}
.hero::before {
  content: ''; position: absolute; inset: 0;
  background: radial-gradient(ellipse at 70% 50%, rgba(59,130,246,.15) 0%, transparent 65%);
}
.hero-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 4rem; align-items: center;
  position: relative; z-index: 1;
}
.hero-label {
  display: inline-flex; align-items: center; gap: .5rem;
  background: rgba(59,130,246,.15); border: 1px solid rgba(59,130,246,.3);
  color: #93c5fd; font-size: .8rem; font-weight: 600; letter-spacing: .06em;
  text-transform: uppercase; padding: .35rem .9rem; border-radius: 100px;
  margin-bottom: 1.25rem;
}
.hero h1 { color: var(--white); margin-bottom: 1.25rem; }
.hero p { color: rgba(255,255,255,.65); font-size: 1.1rem; margin-bottom: 2rem; }
.hero-stats {
  display: flex; gap: 2rem; flex-wrap: wrap;
}
.hero-stat strong { display: block; color: var(--white); font-size: 1.5rem; }
.hero-stat span { color: rgba(255,255,255,.5); font-size: .85rem; }

/* ── Calculator Card ── */
.calc-card {
  background: var(--white); border-radius: 20px;
  box-shadow: 0 20px 80px rgba(0,0,0,.3);
  padding: 2rem; overflow: hidden; position: relative;
}
.calc-card::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 4px;
  background: linear-gradient(90deg, var(--blue), #60a5fa);
}
.calc-title {
  font-size: 1rem; font-weight: 700; color: var(--navy);
  margin-bottom: 1.5rem; display: flex; align-items: center; gap: .5rem;
}
.calc-title span { font-family: var(--mono); background: var(--blue-light); color: var(--blue); padding: .1rem .45rem; border-radius: 4px; font-size: .8rem; }
.calc-fields { display: grid; gap: 1rem; margin-bottom: 1.25rem; }
.field-group label { display: block; font-size: .8rem; font-weight: 600; color: var(--navy-600); text-transform: uppercase; letter-spacing: .05em; margin-bottom: .4rem; }
.field-group input {
  width: 100%; padding: .75rem 1rem; border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm); font-family: var(--mono); font-size: 1rem;
  color: var(--navy); background: var(--gray-50);
  transition: border-color var(--transition), box-shadow var(--transition);
}
.field-group input:focus { outline: none; border-color: var(--blue); box-shadow: 0 0 0 3px rgba(59,130,246,.15); background: white; }
.calc-btn {
  width: 100%; padding: .85rem; background: var(--blue); color: white;
  border: none; border-radius: var(--radius-sm); font-family: var(--font);
  font-size: 1rem; font-weight: 700; cursor: pointer;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
  letter-spacing: -.01em;
}
.calc-btn:hover { background: var(--blue-dark); transform: translateY(-1px); box-shadow: 0 4px 16px rgba(59,130,246,.35); }
.calc-btn:active { transform: translateY(0); }
#calc-result { margin-top: 1.25rem; display: none; }
.result-box {
  border-radius: var(--radius-sm); padding: 1.25rem; text-align: center;
}
.result-box.positive { background: #ecfdf5; border: 2px solid #6ee7b7; }
.result-box.negative { background: #fef2f2; border: 2px solid #fca5a5; }
.result-label { font-size: .8rem; font-weight: 600; text-transform: uppercase; letter-spacing: .06em; margin-bottom: .35rem; }
.result-box.positive .result-label { color: #065f46; }
.result-box.negative .result-label { color: #991b1b; }
.result-value { font-family: var(--mono); font-size: 2rem; font-weight: 500; }
.result-box.positive .result-value { color: var(--green); }
.result-box.negative .result-value { color: var(--red); }
.result-desc { font-size: .85rem; margin-top: .35rem; }
.result-box.positive .result-desc { color: #059669; }
.result-box.negative .result-desc { color: #dc2626; }

/* Step-by-step breakdown */
.breakdown {
  margin-top: 1rem; background: var(--gray-50); border-radius: var(--radius-sm);
  padding: 1rem; border: 1px solid var(--gray-200);
}
.breakdown-title { font-size: .8rem; font-weight: 700; color: var(--navy-700); text-transform: uppercase; letter-spacing: .05em; margin-bottom: .75rem; }
.step { display: flex; gap: .75rem; align-items: flex-start; margin-bottom: .6rem; }
.step:last-child { margin-bottom: 0; }
.step-num {
  min-width: 22px; height: 22px; background: var(--blue); color: white;
  border-radius: 50%; font-size: .7rem; font-weight: 700;
  display: grid; place-items: center; flex-shrink: 0; margin-top: .1rem;
}
.step-text { font-size: .85rem; color: var(--navy-700); }
.step-text code { font-family: var(--mono); background: var(--gray-200); padding: .1rem .3rem; border-radius: 3px; font-size: .8rem; }

/* ── Section Styles ── */
.section-label {
  display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .1em;
  text-transform: uppercase; color: var(--blue); margin-bottom: .75rem;
}
.section-header { margin-bottom: 3rem; }
.section-header p { font-size: 1.1rem; margin-top: .75rem; max-width: 600px; }

/* ── What Is Section ── */
.what-is { background: var(--gray-50); }
.what-is-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 4rem; align-items: center; }
.formula-display {
  background: var(--navy); border-radius: var(--radius); padding: 2rem;
  font-family: var(--mono); position: relative; overflow: hidden;
}
.formula-display::before {
  content: 'FORMULA'; position: absolute; top: 1rem; right: 1rem;
  font-size: .65rem; font-weight: 600; letter-spacing: .12em;
  color: rgba(255,255,255,.25); font-family: var(--font);
}
.formula-line { color: rgba(255,255,255,.5); font-size: .85rem; margin-bottom: .35rem; }
.formula-main { color: #60a5fa; font-size: 1.15rem; font-weight: 500; margin: .75rem 0; border-top: 1px solid rgba(255,255,255,.1); border-bottom: 1px solid rgba(255,255,255,.1); padding: .75rem 0; }
.formula-note { color: rgba(255,255,255,.4); font-size: .78rem; }

/* Feature cards */
.features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
.feature-card {
  background: white; border: 1px solid var(--gray-200); border-radius: var(--radius);
  padding: 1.75rem; transition: transform var(--transition), box-shadow var(--transition);
}
.feature-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); }
.feature-icon { font-size: 1.75rem; margin-bottom: 1rem; }
.feature-card h3 { font-size: 1.05rem; margin-bottom: .5rem; }
.feature-card p { font-size: .9rem; }

/* ── How to Use ── */
.steps-list { counter-reset: steps; display: grid; gap: 1.5rem; max-width: 720px; }
.step-item { display: flex; gap: 1.5rem; align-items: flex-start; }
.step-circle {
  min-width: 48px; height: 48px; background: var(--blue); border-radius: 50%;
  color: white; font-weight: 700; font-size: 1.1rem; display: grid; place-items: center; flex-shrink: 0;
}
.step-item h4 { margin-bottom: .35rem; }
.step-item p { font-size: .95rem; }

/* ── Examples Table ── */
.examples-section { background: var(--gray-50); }
.table-wrap { overflow-x: auto; border-radius: var(--radius); box-shadow: var(--shadow); }
table { width: 100%; border-collapse: collapse; background: white; }
thead { background: var(--navy); }
th { padding: 1rem 1.25rem; text-align: left; color: white; font-size: .85rem; font-weight: 600; letter-spacing: .04em; text-transform: uppercase; }
td { padding: .9rem 1.25rem; font-size: .95rem; border-bottom: 1px solid var(--gray-100); }
tr:last-child td { border-bottom: none; }
tr:hover td { background: var(--gray-50); }
.tag { display: inline-block; padding: .2rem .65rem; border-radius: 100px; font-size: .78rem; font-weight: 600; }
.tag-up { background: #ecfdf5; color: #065f46; }
.tag-down { background: #fef2f2; color: #991b1b; }
.mono-val { font-family: var(--mono); font-weight: 500; }

/* ── Blog Cards ── */
.blog-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.5rem; }
.blog-card {
  background: white; border: 1px solid var(--gray-200); border-radius: var(--radius);
  padding: 1.75rem; display: flex; flex-direction: column;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.blog-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--blue); }
.blog-tag { display: inline-block; font-size: .72rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--blue); margin-bottom: .75rem; }
.blog-card h3 { font-size: 1.1rem; margin-bottom: .6rem; color: var(--navy); }
.blog-card p { font-size: .9rem; flex: 1; }
.blog-link { display: inline-flex; align-items: center; gap: .35rem; margin-top: 1.25rem; font-size: .9rem; font-weight: 600; color: var(--blue); }
.blog-link::after { content: '→'; transition: transform var(--transition); }
.blog-card:hover .blog-link::after { transform: translateX(4px); }

/* ── Footer ── */
footer {
  background: var(--navy); color: rgba(255,255,255,.6);
  padding: 4rem 0 2rem;
}
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 3rem; margin-bottom: 3rem; }
.footer-brand p { font-size: .9rem; margin-top: .75rem; max-width: 280px; }
.footer-brand .logo { margin-bottom: .75rem; }
.footer-col h5 { color: white; font-size: .85rem; font-weight: 700; text-transform: uppercase; letter-spacing: .07em; margin-bottom: 1rem; }
.footer-col a { display: block; color: rgba(255,255,255,.55); font-size: .9rem; margin-bottom: .5rem; transition: color var(--transition); }
.footer-col a:hover { color: white; }
.footer-bottom { border-top: 1px solid rgba(255,255,255,.08); padding-top: 1.5rem; display: flex; justify-content: space-between; align-items: center; font-size: .85rem; }

/* ── Blog Index ── */
.blog-hero { background: var(--navy); padding: 5rem 0; }
.blog-hero h1 { color: white; margin-bottom: .75rem; }
.blog-hero p { color: rgba(255,255,255,.6); font-size: 1.1rem; }
.blog-listing { padding: 5rem 0; }
.blog-listing-grid { display: grid; gap: 2rem; }
.post-card {
  background: white; border: 1px solid var(--gray-200); border-radius: var(--radius);
  padding: 2rem; display: grid; grid-template-columns: 1fr auto; gap: 1.5rem; align-items: center;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.post-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); border-color: var(--blue); }
.post-meta { display: flex; align-items: center; gap: 1rem; margin-bottom: .5rem; flex-wrap: wrap; }
.post-cat { font-size: .75rem; font-weight: 700; text-transform: uppercase; letter-spacing: .07em; color: var(--blue); }
.post-time { font-size: .8rem; color: var(--text-muted); }
.post-card h2 { font-size: 1.25rem; margin-bottom: .5rem; }
.post-card p { font-size: .95rem; }
.read-btn {
  display: inline-flex; align-items: center; gap: .4rem; padding: .65rem 1.4rem;
  background: var(--blue-light); color: var(--blue); border-radius: var(--radius-sm);
  font-weight: 600; font-size: .9rem; white-space: nowrap;
  transition: background var(--transition), color var(--transition);
}
.read-btn:hover { background: var(--blue); color: white; }

/* ── Blog Post ── */
.post-hero { background: var(--navy); padding: 5rem 0; }
.breadcrumb { display: flex; align-items: center; gap: .5rem; margin-bottom: 1.5rem; }
.breadcrumb a { color: rgba(255,255,255,.5); font-size: .85rem; }
.breadcrumb a:hover { color: rgba(255,255,255,.85); }
.breadcrumb span { color: rgba(255,255,255,.25); font-size: .85rem; }
.post-hero h1 { color: white; margin-bottom: 1rem; }
.post-info { display: flex; gap: 1.5rem; flex-wrap: wrap; }
.post-info span { color: rgba(255,255,255,.5); font-size: .9rem; }
.post-body { max-width: 760px; margin: 0 auto; }
.post-content { padding: 4rem 0; }
.post-body h2 { margin: 2.5rem 0 1rem; font-size: 1.5rem; }
.post-body h3 { margin: 2rem 0 .75rem; font-size: 1.15rem; }
.post-body p { margin-bottom: 1.25rem; color: var(--navy-700); line-height: 1.8; }
.post-body ul, .post-body ol { padding-left: 1.5rem; margin-bottom: 1.25rem; }
.post-body li { color: var(--navy-700); margin-bottom: .45rem; line-height: 1.7; }
.post-body strong { color: var(--navy); }
.post-body a { font-weight: 500; }
.post-callout {
  background: var(--blue-light); border-left: 4px solid var(--blue);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 1.25rem 1.5rem; margin: 2rem 0;
}
.post-callout p { color: var(--navy-700); margin: 0; }

/* FAQ */
.faq-section { background: var(--gray-50); padding: 4rem 0; }
.faq-grid { max-width: 760px; margin: 2rem auto 0; display: grid; gap: 1rem; }
.faq-item {
  background: white; border: 1px solid var(--gray-200); border-radius: var(--radius-sm);
  overflow: hidden;
}
.faq-q {
  width: 100%; display: flex; justify-content: space-between; align-items: center;
  padding: 1.1rem 1.25rem; background: none; border: none; cursor: pointer;
  font-family: var(--font); font-size: 1rem; font-weight: 600; color: var(--navy);
  text-align: left; gap: 1rem;
  transition: background var(--transition);
}
.faq-q:hover { background: var(--gray-50); }
.faq-q svg { flex-shrink: 0; transition: transform var(--transition); }
.faq-item.open .faq-q svg { transform: rotate(45deg); }
.faq-a { max-height: 0; overflow: hidden; transition: max-height .35s ease, padding .35s ease; }
.faq-item.open .faq-a { max-height: 300px; }
.faq-a p { padding: 0 1.25rem 1.1rem; color: var(--navy-700); margin: 0; }

/* Related posts */
.related { padding: 4rem 0; border-top: 1px solid var(--gray-200); }
.related-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.25rem; margin-top: 1.5rem; }
.related-card {
  border: 1px solid var(--gray-200); border-radius: var(--radius-sm); padding: 1.25rem;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.related-card:hover { border-color: var(--blue); box-shadow: var(--shadow); }
.related-card h4 { font-size: .95rem; color: var(--navy); margin-bottom: .35rem; }
.related-card span { font-size: .8rem; color: var(--blue); font-weight: 600; }

/* ── Utilities ── */
.text-center { text-align: center; }
.btn {
  display: inline-flex; align-items: center; gap: .5rem;
  padding: .8rem 1.75rem; border-radius: var(--radius-sm);
  font-weight: 700; font-size: 1rem; cursor: pointer;
  transition: all var(--transition);
}
.btn-primary { background: var(--blue); color: white; }
.btn-primary:hover { background: var(--blue-dark); transform: translateY(-1px); box-shadow: 0 4px 16px rgba(59,130,246,.3); color: white; }
.btn-outline { background: transparent; color: var(--blue); border: 2px solid var(--blue); }
.btn-outline:hover { background: var(--blue); color: white; }

/* ── Responsive ── */
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; gap: 2.5rem; }
  .what-is-grid { grid-template-columns: 1fr; gap: 2rem; }
  .features-grid { grid-template-columns: 1fr 1fr; }
  .blog-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .post-card { grid-template-columns: 1fr; }
  .related-grid { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  section { padding: 3.5rem 0; }
  .features-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 2rem; }
  nav a:not(.nav-cta):not(.logo) { display: none; }
  .hero-stats { gap: 1.25rem; }
  .blog-grid { grid-template-columns: 1fr; }
  .what-is-grid { gap: 1.5rem; }
}