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

:root {
  --bg-dark: #1a1525;
  --bg-section: #252038;
  --bg-card: #2d2845;
  --accent: #7ec8e3;
  --accent-warm: #c4a1e0;
  --text-heading: #f0ecf5;
  --text-body: #c8c2d6;
  --text-sub: #9990ab;
  --negative: #f2837b;
  --border: #3d3555;
  --font-stack:
    -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans",
    "Noto Sans JP", sans-serif;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 60px;
}

body {
  font-family: var(--font-stack);
  background: var(--bg-dark);
  color: var(--text-body);
  line-height: 1.6;
}

h1,
h2,
h3 {
  color: var(--text-heading);
  line-height: 1.3;
}

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

/* === Header === */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(26, 21, 37, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-heading);
}

.logo-icon {
  width: 28px;
  height: 28px;
  border-radius: 6px;
}

.logo-text {
  font-weight: 700;
  font-size: 14px;
}

.nav {
  display: flex;
  align-items: center;
  gap: 16px;
  font-size: 13px;
}

.nav a {
  color: var(--text-sub);
  transition: color 0.2s;
}

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

.nav-github {
  display: flex;
  align-items: center;
}

.lang-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 4px 10px;
  color: var(--text-sub);
  font-size: 12px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 4px;
}

.lang-option {
  transition: color 0.2s;
}

.lang-option.active {
  color: var(--accent);
  font-weight: 700;
}

/* === Hero === */
.hero {
  padding: 120px 20px 60px;
  text-align: center;
  background: linear-gradient(
    135deg,
    var(--bg-dark) 0%,
    #1e1835 50%,
    var(--bg-section) 100%
  );
}

.hero-label {
  display: inline-block;
  font-size: 11px;
  letter-spacing: 3px;
  color: var(--accent-warm);
  margin-bottom: 12px;
}

.hero h1 {
  font-size: 28px;
  margin-bottom: 12px;
}

.hero-sub {
  font-size: 16px;
  color: var(--text-sub);
  margin-bottom: 28px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* === CTA Buttons === */
.cta-group {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 24px;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 600;
  transition: opacity 0.2s;
}

.btn:hover {
  opacity: 0.85;
}

.btn-primary {
  background: var(--accent);
  color: #000;
}

/* === Sections === */
.section {
  max-width: 960px;
  margin: 0 auto;
  padding: 60px 20px;
}

.section h2 {
  font-size: 22px;
  text-align: center;
  margin-bottom: 8px;
}

/* === Problem Statement === */
.problem-steps {
  display: flex;
  gap: 20px;
  margin-top: 32px;
}

.problem-step {
  flex: 1;
  background: var(--bg-card);
  padding: 20px 24px;
  border-radius: 12px;
  text-align: center;
  border: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.problem-step--highlight {
  border: 1px solid var(--negative);
  background: rgba(242, 131, 123, 0.1);
}

.problem-step p {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
}

.problem-step-img {
  width: 100%;
  max-width: 200px;
  border-radius: 12px;
  overflow: hidden;
}

.problem-step-img img {
  width: 100%;
  display: block;
  border-radius: 12px;
}

/* === Feature Cards === */
.feature-cards {
  display: flex;
  gap: 16px;
  margin-top: 32px;
}

.feature-card {
  flex: 1;
  background: var(--bg-card);
  padding: 24px;
  border-radius: 12px;
  border: 1px solid var(--border);
}

.feature-card h3 {
  color: var(--accent);
  font-size: 16px;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 13px;
}

.feature-card-img {
  margin-top: 16px;
  border-radius: 6px;
  overflow: hidden;
  aspect-ratio: 9 / 16;
}

.feature-card-img img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: top;
}

/* === Demo Video === */
.demo-video {
  margin-top: 32px;
  text-align: center;
}

.demo-video video {
  width: 100%;
  max-width: 720px;
  border-radius: 12px;
  border: 1px solid var(--border);
}

/* === Target Cards === */
.target-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-top: 32px;
}

.target-card {
  background: var(--bg-card);
  padding: 24px;
  border-radius: 12px;
  border: 1px solid var(--border);
}

.target-card h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.5;
}

.target-card p {
  font-size: 13px;
  color: var(--text-sub);
  line-height: 1.7;
}

/* === Footer === */
.footer {
  text-align: center;
  padding: 60px 20px;
  background: linear-gradient(
    135deg,
    var(--bg-section) 0%,
    #1e1835 50%,
    var(--bg-dark) 100%
  );
}

.footer h2 {
  font-size: 22px;
  margin-bottom: 20px;
}

/* === Requirement Notes === */
.hero-note {
  margin-top: 28px;
  font-size: 12px;
  color: var(--text-sub);
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.8;
  text-align: center;
}

.footer-note {
  margin-top: 16px;
  font-size: 12px;
  color: var(--text-sub);
}

.footer-license {
  margin-top: 8px;
  font-size: 12px;
  color: var(--text-sub);
}

/* === Responsive (mobile) === */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 22px;
  }

  .nav a:not(.nav-github) {
    display: none;
  }

  .problem-steps,
  .feature-cards,
  .setup-steps {
    flex-direction: column;
  }

  .target-cards {
    grid-template-columns: 1fr;
  }
}