:root {
  --bg: #070909;
  --soft: #0d1010;
  --card: #111515;
  --hover: #151a19;
  --border: rgba(255,255,255,.08);
  --border-strong: rgba(255,255,255,.13);
  --text: #f4f7f5;
  --muted: #929b97;
  --green: #7cffb2;
  --green-dark: #54dc8d;
  --danger: #ff7b7b;
  --max: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input {
  font: inherit;
}

.container {
  width: min(var(--max), calc(100% - 48px));
  margin: auto;
}


/* NAVIGATION */

.navbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(7,9,9,.88);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
}

.nav-container {
  width: min(var(--max), calc(100% - 48px));
  height: 72px;
  margin: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 30px;
}

.logo {
  font-size: 18px;
  font-weight: 750;
  letter-spacing: -.4px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  color: var(--muted);
  font-size: 14px;
}

.nav-links a {
  transition: color .2s ease;
}

.nav-links a:hover {
  color: var(--text);
}

.dashboard-btn {
  color: #07100a !important;
  background: var(--green);
  padding: 9px 16px;
  border-radius: 9px;
  font-weight: 650;
}


/* HERO */

.hero {
  padding: 100px 0 52px;
  text-align: center;
}

.hero .container {
  max-width: 800px;
}

.eyebrow {
  display: inline-block;
  color: var(--green);
  font-size: 12px;
  font-weight: 750;
  letter-spacing: 1.7px;
  margin-bottom: 18px;
}

.hero h1 {
  margin: 0;
  font-size: clamp(42px, 7vw, 68px);
  line-height: 1.05;
  letter-spacing: -3px;
}

.hero-description {
  max-width: 650px;
  margin: 24px auto 0;
  color: var(--muted);
  font-size: 18px;
}


/* CALCULATOR */

.calculator-section {
  padding: 20px 0 90px;
}

.calculator-card {
  max-width: 820px;
  margin: auto;
  padding: 38px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 20px;
  box-shadow: 0 25px 70px rgba(0,0,0,.22);
}

.calculator-header {
  margin-bottom: 30px;
}

.calculator-header h2 {
  margin: 0 0 5px;
  font-size: 22px;
  letter-spacing: -.6px;
}

.calculator-header p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.calculator-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.input-group label {
  display: block;
  margin-bottom: 8px;
  color: #c9cfcc;
  font-size: 13px;
  font-weight: 600;
}

.input-wrapper {
  height: 52px;
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 0 16px;
  background: var(--soft);
  border: 1px solid var(--border);
  border-radius: 10px;
  transition: border-color .2s ease, background .2s ease;
}

.input-wrapper:focus-within {
  border-color: rgba(124,255,178,.5);
  background: #101413;
}

.input-wrapper span {
  color: var(--muted);
  font-size: 14px;
}

.input-wrapper input {
  width: 100%;
  height: 100%;
  padding: 0;
  border: 0;
  outline: 0;
  color: var(--text);
  background: transparent;
  font-size: 15px;
}

.input-wrapper input::placeholder {
  color: #59605d;
}

.percentage input {
  order: 1;
}

.percentage span {
  order: 2;
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  opacity: 0;
}

.calculate-btn {
  width: 100%;
  margin-top: 26px;
  padding: 14px 20px;
  border: 0;
  border-radius: 10px;
  color: #07100a;
  background: var(--green);
  font-weight: 750;
  cursor: pointer;
  transition: transform .15s ease, background .2s ease;
}

.calculate-btn:hover {
  background: var(--green-dark);
  transform: translateY(-1px);
}

.calculate-btn:active {
  transform: translateY(0);
}

.error-message {
  min-height: 0;
  margin: 14px 0 0;
  color: var(--danger);
  font-size: 13px;
}

.error-message:empty {
  display: none;
}


/* RESULTS */

.results {
  display: none;
  margin-top: 32px;
  padding-top: 30px;
  border-top: 1px solid var(--border);
}

.results.visible {
  display: block;
}

.main-result {
  padding: 26px;
  margin-bottom: 16px;
  text-align: center;
  background: rgba(124,255,178,.055);
  border: 1px solid rgba(124,255,178,.14);
  border-radius: 14px;
}

.main-result span {
  display: block;
  margin-bottom: 7px;
  color: var(--muted);
  font-size: 13px;
}

.main-result strong {
  display: inline-block;
  color: var(--green);
  font-size: 38px;
  line-height: 1;
  letter-spacing: -1.5px;
}

.main-result small {
  margin-left: 6px;
  color: var(--muted);
  font-size: 13px;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

.result-item {
  padding: 18px;
  background: var(--soft);
  border: 1px solid var(--border);
  border-radius: 11px;
}

.result-item span {
  display: block;
  margin-bottom: 4px;
  color: var(--muted);
  font-size: 12px;
}

.result-item strong {
  font-size: 17px;
  font-weight: 650;
}


/* EDUCATIONAL CONTENT */

.content-section {
  padding: 20px 0 110px;
  border-top: 1px solid var(--border);
}

.content-container {
  width: min(760px, calc(100% - 48px));
  margin: auto;
  padding-top: 80px;
}

.content-container h2 {
  margin: 58px 0 15px;
  font-size: 28px;
  line-height: 1.25;
  letter-spacing: -1px;
}

.content-container h2:first-child {
  margin-top: 0;
}

.content-container p {
  margin: 0 0 18px;
  color: #abb3af;
  font-size: 16px;
}

.formula {
  margin: 26px 0;
  padding: 18px 20px;
  background: var(--card);
  border: 1px solid var(--border);
  border-left: 3px solid var(--green);
  border-radius: 8px;
  color: #e8ecea;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 14px;
}


/* CTA */

.cta-card {
  margin: 70px 0;
  padding: 38px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 18px;
}

.cta-card > span {
  color: var(--green);
  font-size: 11px;
  font-weight: 750;
  letter-spacing: 1.5px;
}

.cta-card h2 {
  margin: 10px 0 12px;
  font-size: 27px;
}

.cta-card p {
  max-width: 580px;
}

.cta-button {
  display: inline-block;
  margin-top: 8px;
  padding: 11px 18px;
  color: #07100a;
  background: var(--green);
  border-radius: 9px;
  font-size: 14px;
  font-weight: 700;
  transition: background .2s ease, transform .2s ease;
}

.cta-button:hover {
  background: var(--green-dark);
  transform: translateY(-1px);
}


/* FAQ */

.faq {
  margin-top: 70px;
}

.faq-item {
  padding: 24px 0;
  border-bottom: 1px solid var(--border);
}

.faq-item h3 {
  margin: 0 0 8px;
  font-size: 17px;
}

.faq-item p {
  margin: 0;
  font-size: 15px;
}


/* FOOTER */

footer {
  border-top: 1px solid var(--border);
}

.footer-container {
  width: min(var(--max), calc(100% - 48px));
  min-height: 100px;
  margin: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 30px;
  color: var(--muted);
  font-size: 13px;
}

.footer-container div {
  display: flex;
  gap: 22px;
}

.footer-container a:hover {
  color: var(--text);
}


/* MOBILE */

@media (max-width: 700px) {

  .nav-container {
    width: min(100% - 30px, var(--max));
  }

  .nav-links {
    gap: 15px;
  }

  .nav-links > a:not(.dashboard-btn) {
    display: none;
  }

  .hero {
    padding: 72px 0 40px;
  }

  .hero h1 {
    letter-spacing: -2px;
  }

  .hero-description {
    font-size: 16px;
  }

  .container {
    width: calc(100% - 30px);
  }

  .calculator-card {
    padding: 24px 18px;
    border-radius: 15px;
  }

  .calculator-grid {
    grid-template-columns: 1fr;
  }

  .result-grid {
    grid-template-columns: 1fr;
  }

  .content-container {
    width: calc(100% - 34px);
    padding-top: 60px;
  }

  .content-container h2 {
    font-size: 24px;
  }

  .cta-card {
    padding: 26px 22px;
  }

  .footer-container {
    width: calc(100% - 30px);
    padding: 30px 0;
    flex-direction: column;
    align-items: flex-start;
  }
}