/* ========================================
   株式会社Letter コーポレートサイト
   Mobile-First Responsive CSS
   Design: Navy header, Orange CTA, White base
   ======================================== */

/* ========== CSS Variables ========== */
:root {
  /* Colors - Updated Design */
  --color-primary: #1E3A5F;
  /* Navy - 見出し */
  --color-primary-dark: #152A45;
  --color-primary-light: #2A4A73;
  --color-accent: #3B82F6;
  /* 瀬戸内ブルー - アクセント */
  --color-cta: #F97316;
  /* オレンジ - CTA */
  --color-cta-dark: #EA580C;

  --color-bg-dark: #0A1628;
  /* Header背景 */
  --color-bg-darker: #060F1D;
  --color-bg-light: #FFFFFF;
  /* 白ベース */
  --color-bg-alt: #F8FAFC;
  /* セクション背景 */

  --color-text-dark: #1E293B;
  /* 本文ダークグレー */
  --color-text-body: #475569;
  --color-text-light: #64748B;
  --color-text-white: #FFFFFF;
  --color-text-on-dark: #E2E8F0;

  --color-border: #E2E8F0;
  --color-border-dark: #1E293B;

  /* Typography */
  --font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;

  /* Spacing - 余白を増やして読みやすく */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;
  --space-5xl: 8rem;

  /* Layout */
  --container-max: 1200px;
  --container-padding: 1.25rem;

  /* Effects */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);

  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  --transition: 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.8;
  color: var(--color-text-body);
  background-color: var(--color-bg-light);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

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

ul,
ol {
  list-style: none;
}

/* ========== Utility Classes ========== */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

.section {
  padding: var(--space-3xl) 0;
}

.section--alt {
  background-color: var(--color-bg-alt);
}

.section__header {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.section__header--left {
  text-align: left;
}

.section__label {
  display: inline-block;
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: var(--space-sm);
}

.section__title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1.4;
}

.section__desc {
  margin-top: var(--space-md);
  color: var(--color-text-light);
  max-width: 640px;
  margin-left: auto;
  margin-right: auto;
}

/* ========== Buttons ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.875rem 1.75rem;
  font-size: var(--font-size-sm);
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition);
  text-align: center;
  white-space: nowrap;
}

.btn--primary {
  background-color: var(--color-accent);
  color: var(--color-text-white);
  border-color: var(--color-accent);
}

.btn--primary:hover {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* CTA ボタン（オレンジ） */
.btn--cta {
  background-color: var(--color-cta);
  color: var(--color-text-white);
  border-color: var(--color-cta);
}

.btn--cta:hover {
  background-color: var(--color-cta-dark);
  border-color: var(--color-cta-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn--outline {
  background-color: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn--outline:hover {
  background-color: var(--color-primary);
  color: var(--color-text-white);
}

.btn--large {
  padding: 1rem 2.5rem;
  font-size: var(--font-size-base);
}

.btn--header {
  padding: 0.5rem 1rem;
  background-color: var(--color-cta);
  color: var(--color-text-white);
  border-color: var(--color-cta);
}

.btn--header:hover {
  background-color: var(--color-cta-dark);
  border-color: var(--color-cta-dark);
}



/* ========== Header ========== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background-color: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
}

.header__container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

.header__logo-text {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: 0.05em;
}

/* Mobile Navigation */
.header__nav-toggle {
  display: none;
}

.header__nav-label {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 6px;
  width: 32px;
  height: 32px;
  cursor: pointer;
  z-index: 1001;
  padding: 4px;
}

.header__nav-label span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--color-primary);
  transition: all var(--transition);
  border-radius: 1px;
}

.header__nav-list {
  position: fixed;
  top: 0;
  right: -100%;
  width: 85%;
  max-width: 320px;
  height: 100vh;
  background-color: var(--color-bg-dark);
  padding: 100px var(--space-xl) var(--space-xl);
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  transition: right var(--transition);
  overflow-y: auto;
}

.header__nav-list li {
  border-bottom: 1px solid var(--color-border-dark);
  padding-bottom: var(--space-md);
}

.header__nav-list li:last-child {
  border-bottom: none;
  padding-bottom: 0;
  margin-top: var(--space-md);
}

.header__nav-list a {
  color: var(--color-text-on-dark);
  font-size: var(--font-size-base);
  font-weight: 500;
  transition: color var(--transition);
  display: block;
  white-space: nowrap;
}

.header__nav-list a:hover {
  color: var(--color-cta);
}

.header__nav-toggle:checked~.header__nav-list {
  right: 0;
}

.header__nav-toggle:checked~.header__nav-label span:nth-child(1) {
  transform: rotate(45deg) translate(6px, 6px);
}

.header__nav-toggle:checked~.header__nav-label span:nth-child(2) {
  opacity: 0;
}

.header__nav-toggle:checked~.header__nav-label span:nth-child(3) {
  transform: rotate(-45deg) translate(6px, -6px);
}

/* Mobile Menu Overlay */
.header__nav-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 999;
}

.header__nav-toggle:checked~.header__nav-overlay {
  display: block;
}


/* ========== Hero Section ========== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  background: var(--color-bg-light);
  overflow: hidden;
  padding-top: 70px;
}

.hero__container {
  display: flex;
  flex-direction: column;
  gap: var(--space-2xl);
  position: relative;
  z-index: 2;
}

.hero__content {
  text-align: center;
}

.hero__title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1.5;
  margin-bottom: var(--space-lg);
}

.hero__title-accent {
  color: var(--color-accent);
}

.hero__subtitle {
  font-size: var(--font-size-base);
  color: var(--color-text-body);
  margin-bottom: var(--space-xl);
  line-height: 2;
}

.hero__cta {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.hero__cta .btn--outline {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.hero__cta .btn--outline:hover {
  background-color: var(--color-primary);
  color: var(--color-text-white);
}

.hero__visual {
  display: flex;
  justify-content: center;
}

.hero__image-placeholder {
  width: 100%;
  max-width: 400px;
  aspect-ratio: 4/3;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.15) 0%, rgba(59, 200, 230, 0.1) 100%);
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-light);
  font-size: var(--font-size-sm);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-lg);
}

.hero__bg-gradient {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background:
    radial-gradient(circle at 10% 90%, rgba(59, 130, 246, 0.08) 0%, transparent 50%),
    radial-gradient(circle at 90% 10%, rgba(59, 200, 230, 0.06) 0%, transparent 50%);
  z-index: 1;
}

/* ========== About Section ========== */
.about__content {
  display: flex;
  flex-direction: column;
  gap: var(--space-2xl);
}

.about__lead {
  font-size: var(--font-size-lg);
  color: var(--color-text-dark);
  margin-bottom: var(--space-md);
  line-height: 1.9;
}

.about__lead strong {
  color: var(--color-primary);
}

.about__text p {
  margin-bottom: var(--space-md);
  line-height: 1.9;
}

.about__stance {
  margin-top: var(--space-xl);
  padding: var(--space-lg);
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-lg);
  border-left: 4px solid var(--color-cta);
}

.about__stance ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.about__stance li {
  position: relative;
  padding-left: var(--space-lg);
  font-size: var(--font-size-sm);
  color: var(--color-text-dark);
  font-weight: 500;
}

.about__stance li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--color-cta);
  font-weight: 700;
}

/* ========== Service Section ========== */
.service__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

.service-card {
  background-color: var(--color-bg-light);
  padding: var(--space-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  transition: all var(--transition);
}

.service-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
}

.service-card__icon {
  width: 56px;
  height: 56px;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
}

.service-card__icon svg {
  width: 28px;
  height: 28px;
  color: var(--color-text-white);
}

.service-card__title {
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1.5;
  margin-bottom: var(--space-md);
}

.service-card__title small {
  display: block;
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-light);
  margin-top: var(--space-xs);
}

.service-card__desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-body);
  margin-bottom: var(--space-lg);
  line-height: 1.8;
}

.service-card__link {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-accent);
}

.service-card__link:hover {
  color: var(--color-primary);
}

.service__note {
  margin-top: var(--space-2xl);
  padding: var(--space-lg);
  background-color: var(--color-bg-light);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
}

.service__note p {
  font-size: var(--font-size-sm);
  color: var(--color-text-body);
  line-height: 1.7;
}

.service__note strong {
  color: var(--color-primary);
}

/* ========== Why Choose Us Section ========== */
.why__content {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.why__points {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.why__point {
  display: flex;
  gap: var(--space-lg);
  align-items: flex-start;
  padding: var(--space-lg);
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-lg);
}

.why__point-icon {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--color-text-white);
}

.why__point-content h3 {
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-sm);
  line-height: 1.5;
}

.why__point-content p {
  font-size: var(--font-size-sm);
  color: var(--color-text-body);
  line-height: 1.8;
}

/* ========== CEO Section ========== */
.ceo__content {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.ceo__image {
  display: flex;
  justify-content: center;
}

.ceo__image-placeholder {
  width: 180px;
  height: 180px;
  background: linear-gradient(135deg, var(--color-border) 0%, var(--color-bg-alt) 100%);
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-light);
  font-size: var(--font-size-sm);
}

.ceo__text {
  text-align: center;
}

.ceo__name {
  margin-bottom: var(--space-xl);
}

.ceo__name-position {
  display: block;
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin-bottom: var(--space-xs);
}

.ceo__name-full {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--color-primary);
}

.ceo__bio {
  text-align: left;
}

.ceo__bio p {
  font-size: var(--font-size-sm);
  color: var(--color-text-body);
  margin-bottom: var(--space-md);
  line-height: 2;
}

.ceo__bio p:last-child {
  margin-bottom: 0;
}

/* ========== Media Section ========== */
.media__empty {
  text-align: center;
  padding: var(--space-2xl);
  background-color: var(--color-bg-alt);
  border-radius: var(--radius-lg);
}

.media__empty p {
  color: var(--color-text-light);
  margin-bottom: var(--space-lg);
}

/* ========== News Section ========== */
.news__empty {
  text-align: center;
  padding: var(--space-xl);
  background-color: var(--color-bg-light);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-xl);
}

.news__empty p {
  color: var(--color-text-light);
}

.news__list {
  border-top: 1px solid var(--color-border);
}

.news__item {
  border-bottom: 1px solid var(--color-border);
}

.news__item a {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-sm) var(--space-md);
  padding: var(--space-lg) 0;
  transition: background-color var(--transition);
}

.news__item a:hover {
  background-color: rgba(59, 130, 246, 0.05);
}

.news__date {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  flex-shrink: 0;
}

.news__tag {
  display: inline-block;
  padding: var(--space-xs) var(--space-sm);
  font-size: var(--font-size-xs);
  font-weight: 500;
  color: var(--color-accent);
  background-color: rgba(59, 130, 246, 0.1);
  border-radius: var(--radius-sm);
  flex-shrink: 0;
}

.news__title {
  font-size: var(--font-size-sm);
  color: var(--color-text-dark);
  width: 100%;
}

.news__more {
  margin-top: var(--space-xl);
  text-align: center;
}

/* ========== Contact Section ========== */
.contact {
  background: linear-gradient(135deg, var(--color-bg-dark) 0%, var(--color-bg-darker) 100%);
}

.contact__container {
  display: flex;
  flex-direction: column;
  gap: var(--space-2xl);
}

.contact .section__label {
  color: var(--color-cta);
}

.contact .section__title {
  color: var(--color-text-white);
}

.contact__text {
  color: var(--color-text-on-dark);
  margin-bottom: var(--space-xl);
  line-height: 2;
}

.contact__visual {
  display: flex;
  justify-content: center;
}

.contact__image-placeholder {
  width: 100%;
  max-width: 300px;
  aspect-ratio: 1;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.3) 0%, rgba(249, 115, 22, 0.2) 100%);
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-on-dark);
  font-size: var(--font-size-sm);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

/* ========== Footer ========== */
.footer {
  background-color: var(--color-bg-darker);
  padding: var(--space-3xl) 0 var(--space-xl);
}

.footer__main {
  display: flex;
  flex-direction: column;
  gap: var(--space-2xl);
  margin-bottom: var(--space-2xl);
}

.footer__logo {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text-white);
  letter-spacing: 0.05em;
}

.footer__tagline {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin-top: var(--space-sm);
}

.footer__nav {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-xl);
}

.footer__nav-title {
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--color-text-white);
  margin-bottom: var(--space-md);
}

.footer__nav-group ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer__nav-group a {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
}

.footer__nav-group a:hover {
  color: var(--color-text-white);
}

.footer__bottom {
  padding-top: var(--space-xl);
  border-top: 1px solid var(--color-border-dark);
}

.footer__copyright {
  font-size: var(--font-size-xs);
  color: var(--color-text-light);
  text-align: center;
}

/* ========== Responsive: Tablet (768px+) ========== */
@media (min-width: 768px) {
  :root {
    --container-padding: 2rem;
  }

  .section {
    padding: var(--space-4xl) 0;
  }

  .section__title {
    font-size: var(--font-size-3xl);
  }

  /* Header */
  .header__nav-label {
    display: none;
  }

  .header__nav-list {
    position: static;
    width: auto;
    max-width: none;
    height: auto;
    background: transparent;
    padding: 0;
    flex-direction: row;
    gap: var(--space-lg);
    align-items: center;
    overflow: visible;
  }

  .header__nav-list li {
    border-bottom: none;
    padding-bottom: 0;
  }

  .header__nav-list li:last-child {
    margin-top: 0;
  }

  .header__nav-list a {
    font-size: var(--font-size-sm);
    color: var(--color-text-dark);
  }

  /* Hero */
  .hero__title {
    font-size: var(--font-size-3xl);
  }

  .hero__subtitle {
    font-size: var(--font-size-lg);
  }

  .hero__cta {
    flex-direction: row;
    justify-content: center;
    gap: var(--space-lg);
  }

  /* Service */
  .service__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .service-card__title {
    font-size: var(--font-size-lg);
  }

  /* Why */
  .why__points {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
  }

  /* CEO */
  .ceo__content {
    flex-direction: row;
    align-items: flex-start;
    gap: var(--space-3xl);
  }

  .ceo__image-placeholder {
    width: 220px;
    height: 220px;
  }

  .ceo__text {
    text-align: left;
    flex: 1;
  }

  .ceo__name {
    text-align: left;
  }

  /* News */
  .news__item a {
    flex-wrap: nowrap;
  }

  .news__title {
    width: auto;
    flex: 1;
  }

  /* Contact */
  .contact__container {
    flex-direction: row;
    align-items: center;
  }

  .contact__content {
    flex: 1;
  }

  .contact__visual {
    flex: 1;
  }

  /* Footer */
  .footer__main {
    flex-direction: row;
    justify-content: space-between;
  }

  .footer__nav {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-3xl);
  }
}

/* ========== Responsive: Desktop (1024px+) ========== */
@media (min-width: 1024px) {
  .section {
    padding: var(--space-5xl) 0;
  }

  .section__title {
    font-size: var(--font-size-4xl);
  }

  /* Header - 余裕を持たせる */
  .header__nav-list {
    gap: var(--space-md);
  }



  /* Hero */
  .hero__container {
    flex-direction: row;
    align-items: center;
    gap: var(--space-3xl);
  }

  .hero__content {
    text-align: left;
    flex: 1;
  }

  .hero__title {
    font-size: var(--font-size-4xl);
  }

  .hero__cta {
    justify-content: flex-start;
  }

  .hero__visual {
    flex: 1;
  }

  .hero__image-placeholder {
    max-width: 500px;
    aspect-ratio: 1;
  }

  /* About */
  .about__lead {
    font-size: var(--font-size-xl);
  }

  /* Service */
  .service__grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* ========== Responsive: Large Desktop (1280px+) ========== */
@media (min-width: 1280px) {
  :root {
    --container-max: 1280px;
  }

  .hero__title {
    font-size: var(--font-size-5xl);
  }
}