:root {
  --bg: #f7f7f5;
  --surface: #ffffff;
  --text: #171717;
  --muted: #666666;
  --border: #e3e3df;
  --accent: #111111;
  --max-width: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

a {
  color: inherit;
}

.container {
  width: min(92%, var(--max-width));
  margin: 0 auto;
}

header {
  background: rgba(255, 255, 255, 0.95);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
}

header .container {
  min-height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.logo {
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  text-decoration: none;
}

nav {
  display: flex;
  gap: 24px;
}

nav a {
  text-decoration: none;
  color: var(--muted);
  font-size: 0.95rem;
}

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

.hero {
  padding: 110px 0 90px;
  text-align: center;
}

.hero .container {
  max-width: 820px;
}

.eyebrow {
  margin: 0 0 16px;
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  color: var(--muted);
}

h1 {
  margin: 0;
  font-size: clamp(2.6rem, 7vw, 5.5rem);
  line-height: 0.98;
  letter-spacing: -0.055em;
}

.hero-text {
  max-width: 650px;
  margin: 28px auto;
  font-size: 1.15rem;
  color: var(--muted);
}

.primary-button {
  display: inline-block;
  padding: 14px 22px;
  background: var(--accent);
  color: white;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 700;
}

.primary-button:hover {
  opacity: 0.85;
}

section {
  padding: 80px 0;
}

section h2 {
  margin: 0 0 34px;
  font-size: clamp(2rem, 4vw, 3.2rem);
  letter-spacing: -0.035em;
}

.tool-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.tool-card,
.product-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 28px;
}

.tool-card h3,
.product-card h3 {
  margin-top: 0;
  font-size: 1.3rem;
}

.tool-card p,
.product-card p,
#about p {
  color: var(--muted);
}

.tool-card a,
.product-card a {
  display: inline-block;
  margin-top: 12px;
  font-weight: 700;
  text-decoration: none;
}

.tool-card a:hover,
.product-card a:hover {
  text-decoration: underline;
}

.product-card {
  max-width: 720px;
}

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

#about p {
  max-width: 700px;
  font-size: 1.1rem;
}

footer {
  border-top: 1px solid var(--border);
  padding: 28px 0;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 800px) {
  header .container {
    min-height: 64px;
  }

  nav {
    gap: 14px;
  }

  nav a {
    font-size: 0.85rem;
  }

  .hero {
    padding: 80px 0 65px;
  }

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

  section {
    padding: 60px 0;
  }
}

@media (max-width: 520px) {
  header .container {
    align-items: flex-start;
    padding-top: 18px;
    padding-bottom: 18px;
    flex-direction: column;
    gap: 10px;
  }

  nav {
    width: 100%;
    justify-content: space-between;
  }

  h1 {
    font-size: 2.8rem;
  }

  .hero-text {
    font-size: 1rem;
  }
}

.calculator-section {
  padding: 72px 0 96px;
}

.calculator-container {
  max-width: 980px;
}

.calculator-title {
  max-width: 820px;
  font-size: clamp(2.5rem, 6vw, 4.6rem);
  line-height: 1;
  margin-bottom: 22px;
}

.calculator-intro {
  max-width: 720px;
  color: var(--muted);
  font-size: 1.1rem;
  margin-bottom: 42px;
}

.calculator-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
  align-items: start;
}

.calculator-card,
.result-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 30px;
}

.calculator-card {
  display: grid;
  gap: 12px;
}

.calculator-card label {
  font-weight: 700;
  margin-top: 8px;
}

.calculator-card input {
  width: 100%;
  min-height: 48px;
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 0 14px;
  font: inherit;
  background: #fff;
  color: var(--text);
}

.calculator-card input:focus {
  outline: 2px solid #111;
  outline-offset: 2px;
}

.input-group {
  display: flex;
  align-items: center;
  min-height: 48px;
  border: 1px solid var(--border);
  border-radius: 9px;
  background: #fff;
  overflow: hidden;
}

.input-group span {
  padding-left: 14px;
  color: var(--muted);
  font-weight: 700;
}

.input-group input {
  border: 0;
}

.input-group input:focus {
  outline: none;
}

.calculator-button {
  border: 0;
  cursor: pointer;
  margin-top: 18px;
  min-height: 50px;
  font-size: 1rem;
}

.result-card {
  position: sticky;
  top: 100px;
}

.result-label {
  color: var(--muted);
  margin-bottom: 6px;
}

.result-number {
  margin: 0 0 24px;
  font-size: clamp(2.8rem, 6vw, 4.4rem);
  line-height: 1;
  font-weight: 800;
  letter-spacing: -0.05em;
}

.result-details {
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  padding: 14px 0;
}

.result-details p {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  margin: 10px 0;
}

.calculator-note {
  margin-top: 20px;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 800px) {
  .calculator-layout {
    grid-template-columns: 1fr;
  }

  .result-card {
    position: static;
  }

  .calculator-section {
    padding-top: 48px;
  }
}

.product-page {
  padding: 72px 0 100px;
}

.product-page-container {
  max-width: 980px;
}

.product-title {
  font-size: clamp(2.7rem, 6vw, 5rem);
  line-height: 1;
  margin: 0 0 24px;
}

.product-intro {
  max-width: 760px;
  color: var(--muted);
  font-size: 1.15rem;
  margin-bottom: 48px;
}

.product-layout {
  display: grid;
  grid-template-columns: 1.4fr 0.8fr;
  gap: 36px;
  align-items: start;
}

.product-main h2 {
  margin-top: 0;
  margin-bottom: 14px;
  font-size: 1.7rem;
}

.product-main p {
  color: var(--muted);
  margin-bottom: 34px;
}

.product-list {
  margin: 0 0 40px;
  padding-left: 20px;
}

.product-list li {
  margin-bottom: 12px;
}

.product-buy-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 30px;
  position: sticky;
  top: 100px;
}

.product-price {
  font-size: 3rem;
  font-weight: 800;
  margin: 0 0 16px;
}

.product-disabled-button {
  width: 100%;
  border: 0;
  opacity: 0.5;
  cursor: not-allowed;
}

@media (max-width: 800px) {
  .product-layout {
    grid-template-columns: 1fr;
  }

  .product-buy-card {
    position: static;
  }
}

.legal-page {
  padding: 72px 0 100px;
}

.legal-container {
  max-width: 820px;
}

.legal-container h1 {
  margin-bottom: 14px;
}

.legal-container h2 {
  margin-top: 42px;
  margin-bottom: 12px;
  font-size: 1.4rem;
}

.legal-container p {
  color: var(--muted);
}

.legal-container a {
  font-weight: 700;
}

.legal-updated {
  margin-bottom: 48px;
}

.contact-card {
  margin-top: 40px;
  padding: 30px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
}

.contact-email {
  font-size: clamp(1.3rem, 4vw, 2rem);
  text-decoration: none;
}

footer a {
  color: var(--muted);
  text-decoration: none;
}

footer a:hover {
  color: var(--text);
  text-decoration: underline;
}

.guide-section {
  padding: 80px 0 100px;
}

.guide-container {
  max-width: 880px;
}

.guide-container h2 {
  margin-top: 52px;
  margin-bottom: 18px;
}

.guide-container h2:first-of-type {
  margin-top: 0;
}

.guide-container h3 {
  margin-top: 34px;
  margin-bottom: 12px;
}

.guide-container p,
.guide-container li {
  line-height: 1.75;
  color: var(--muted);
}

.formula-box {
  margin: 24px 0;
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  line-height: 1.8;
}

.guide-links {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.guide-links a {
  font-weight: 700;
  text-decoration: none;
}

.guide-links a:hover {
  text-decoration: underline;
}

.guide-links span {
  margin: 0 10px;
}