/* ========================================================================
   0. リセット & 変数定義
   ======================================================================== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  /* ベースカラー（ライトモード：白ベース） */
  --color-bg: #ffffff;
  --color-bg-alt: #f7f5f5;
  --color-surface: #ffffff;
  --color-text: #1a1a1a;
  --color-text-muted: #5c5555;
  --color-border: #e8e3e3;

  /* アクセントカラー（赤） */
  --color-accent: #d7263d;
  --color-accent-dark: #a81d30;
  --color-accent-light: #fdecec;

  --color-header-bg: rgba(255, 255, 255, 0.9);

  --shadow-card: 0 2px 10px rgba(26, 26, 26, 0.07);
  --shadow-card-hover: 0 10px 24px rgba(26, 26, 26, 0.12);

  --radius: 12px;
  --max-width: 1080px;

  --transition: 0.2s ease;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Yu Gothic", "Noto Sans JP", -apple-system, BlinkMacSystemFont, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
  transition: background-color var(--transition), color var(--transition);
}

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

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

ul,
ol {
  list-style: none;
}

/* キーボード操作時のフォーカス表示 */
a:focus-visible,
button:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 3px;
}

/* prefers-reduced-motion対応：アニメーションを最小化 */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

.section-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  position: relative;
  padding: 96px 0;
}

.section-title {
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  margin-bottom: 48px;
  position: relative;
  padding-bottom: 16px;
}

.section-title::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 48px;
  height: 4px;
  background-color: var(--color-accent);
  border-radius: 2px;
}

/* ========================================================================
   1. ヘッダー
   ======================================================================== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-header-bg);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.nav-list {
  display: flex;
  gap: 28px;
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 500;
  position: relative;
  padding: 4px 2px;
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 0;
  height: 2px;
  background-color: var(--color-accent);
  transition: width var(--transition);
}

.nav-link:hover::after,
.nav-link:focus-visible::after {
  width: 100%;
}

.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
}

.hamburger-line {
  width: 24px;
  height: 2px;
  background-color: var(--color-text);
  transition: transform var(--transition), opacity var(--transition);
}

/* ハンバーガーメニューが開いているときのアイコン変形 */
.hamburger[aria-expanded="true"] .hamburger-line:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.hamburger[aria-expanded="true"] .hamburger-line:nth-child(2) {
  opacity: 0;
}
.hamburger[aria-expanded="true"] .hamburger-line:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ========================================================================
   2. Heroセクション
   ======================================================================== */
.hero {
  position: relative;
  min-height: 88vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  padding: 48px 24px;
  text-align: center;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 720px;
}

.hero-title {
  font-size: clamp(1.7rem, 4.5vw, 2.8rem);
  font-weight: 700;
  line-height: 1.5;
  margin-bottom: 24px;
}

.hero-subtitle {
  font-size: clamp(1rem, 2.2vw, 1.2rem);
  color: var(--color-text-muted);
  margin-bottom: 40px;
}

.scroll-down {
  position: absolute;
  left: 50%;
  bottom: 10px;
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 60px;
  height: 60px;
  border-radius: 50%;
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  transform: translateX(-50%);
  animation: scroll-down-bounce 2.2s ease-in-out infinite;
  transition: color var(--transition), border-color var(--transition);
}

.scroll-down:hover,
.scroll-down:focus-visible {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

@keyframes scroll-down-bounce {
  0%, 100% { transform: translate(-50%, 0); }
  50% { transform: translate(-50%, 6px); }
}

@media (prefers-reduced-motion: reduce) {
  .scroll-down {
    animation: none;
  }
}

/* ボタン共通スタイル */
.btn {
  display: inline-block;
  padding: 13px 28px;
  border-radius: 8px;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  border: 2px solid transparent;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), background-color var(--transition), color var(--transition);
}

.btn:hover,
.btn:focus-visible {
  transform: translateY(-3px);
}

.btn-secondary {
  background-color: var(--color-accent-light);
  color: var(--color-accent);
}

.btn-secondary:hover,
.btn-secondary:focus-visible {
  box-shadow: var(--shadow-card-hover);
}

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

.btn-outline:hover,
.btn-outline:focus-visible {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn-disabled {
  color: var(--color-text-muted);
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-disabled:hover,
.btn-disabled:focus-visible {
  border-color: var(--color-border);
  color: var(--color-text-muted);
  transform: none;
}

/* ========================================================================
   3. Aboutセクション
   ======================================================================== */
.about {
  background-color: var(--color-bg-alt);
}

.about-content {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 56px;
  align-items: start;
}

.about-photo img {
  width: 100%;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  background-color: var(--color-surface);
}

.about-text p {
  color: var(--color-text-muted);
  margin-bottom: 32px;
  font-size: 1.02rem;
}

.about-info {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.about-info-item {
  display: grid;
  grid-template-columns: 140px 1fr;
  gap: 12px;
}

.about-info-item dt {
  font-weight: 700;
  color: var(--color-text);
}

.about-info-item dd {
  color: var(--color-text-muted);
}

.interest-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.interest-list li {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  padding: 4px 12px;
  border-radius: 6px;
  font-size: 0.9rem;
}

/* ========================================================================
   4. Careerセクション
   ======================================================================== */
.timeline {
  position: relative;
  margin-left: 8px;
  border-left: 2px solid var(--color-border);
}

.timeline-item {
  position: relative;
  padding: 0 0 40px 32px;
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-marker {
  position: absolute;
  left: -7px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background-color: var(--color-accent);
  border: 3px solid var(--color-bg);
}

.timeline-date {
  display: block;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--color-text-muted);
  margin-bottom: 6px;
}

.timeline-title {
  font-size: 1.3rem;
  font-weight: 700;
  line-height: 1.5;
}

.aboutline {
  display: block;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: var(--color-text-muted);
  margin-bottom: 6px;
}

/* ========================================================================
   5. Researchセクション
   ======================================================================== */
.research .section-inner + .section-inner {
  margin-top: 32px;
}

.research-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 40px;
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition), transform var(--transition);
}

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

.research-theme {
  font-size: 1.3rem;
  margin-bottom: 16px;
}

.research-desc {
  color: var(--color-text-muted);
  margin-bottom: 24px;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 24px;
}

.tag {
  background-color: var(--color-accent-light);
  color: var(--color-accent);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 6px 14px;
  border-radius: 999px;
}

/* ========================================================================
   6. Projectsセクション
   ======================================================================== */
.coming-soon {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 160px;
  border: 1px dashed var(--color-border);
  border-radius: var(--radius);
}

.coming-soon-text {
  color: var(--color-text-muted);
  font-size: 1rem;
}

.project-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 32px;
}

.project-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-card);
  overflow: hidden;
  transition: box-shadow var(--transition), transform var(--transition);
}

.project-card:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-6px);
}

.project-card-body {
  padding: 32px;
}

.project-title {
  font-size: 1.2rem;
  margin-bottom: 12px;
}

.project-desc {
  color: var(--color-text-muted);
  margin-bottom: 20px;
}

.project-subheading {
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  margin-bottom: 10px;
  margin-top: 20px;
}

.feature-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.feature-list li::before {
  content: "・";
  color: var(--color-accent);
}

.project-card-footer {
  display: flex;
  gap: 12px;
  padding: 24px 32px;
  border-top: 1px solid var(--color-border);
}

.project-card-footer .btn {
  flex: 1;
  text-align: center;
  padding: 10px 16px;
  font-size: 0.9rem;
}

/* ========================================================================
   7. Skillsセクション
   ======================================================================== */
.skills {
  background-color: var(--color-bg-alt);
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 24px;
}

.skill-category {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition), transform var(--transition);
}

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

.skill-category-title {
  font-size: 1.05rem;
  margin-bottom: 16px;
  color: var(--color-accent);
}

/* ========================================================================
   8. Contactセクション
   ======================================================================== */
.contact-text {
  color: var(--color-text-muted);
  margin-bottom: 32px;
  font-size: 1.05rem;
}

.contact-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 480px;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 20px 24px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition), transform var(--transition);
}

.contact-item:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-3px);
}

.contact-label {
  font-weight: 700;
  min-width: 70px;
}

.contact-link {
  color: var(--color-accent);
  word-break: break-all;
}

.contact-link:hover,
.contact-link:focus-visible {
  text-decoration: underline;
}

/* ========================================================================
   9. フッター
   ======================================================================== */
.footer {
  border-top: 1px solid var(--color-border);
  background-color: var(--color-bg-alt);
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.footer-copyright {
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.footer-links {
  display: flex;
  align-items: center;
  gap: 20px;
}

.footer-link {
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.footer-link:hover,
.footer-link:focus-visible {
  color: var(--color-accent);
}

.footer-top-btn {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  padding: 8px 14px;
  font-size: 0.85rem;
  cursor: pointer;
  color: var(--color-text);
  transition: transform var(--transition), background-color var(--transition);
}

.footer-top-btn:hover,
.footer-top-btn:focus-visible {
  background-color: var(--color-accent-light);
  color: var(--color-accent);
  transform: translateY(-3px);
}

/* ========================================================================
   10. レスポンシブ対応（タブレット）
   ======================================================================== */
@media (max-width: 900px) {
  .about-content {
    grid-template-columns: 1fr;
  }

  .about-photo {
    max-width: 220px;
  }
}

/* ========================================================================
   11. レスポンシブ対応（スマートフォン）
   ======================================================================== */
@media (max-width: 720px) {
  .section {
    padding: 64px 0;
  }

  .hamburger {
    display: flex;
  }

  .nav {
    position: fixed;
    top: 65px;
    right: 0;
    left: 0;
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px 24px 24px;
    transform: translateY(-12px);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition), opacity var(--transition), visibility var(--transition);
  }

  /* JavaScriptでnavに付与される開閉クラス */
  .nav.is-open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-list {
    flex-direction: column;
    gap: 4px;
  }

  .nav-link {
    display: block;
    padding: 14px 4px;
    border-bottom: 1px solid var(--color-border);
  }

  .about-info-item {
    grid-template-columns: 1fr;
    gap: 6px;
  }

  .project-card-footer {
    flex-direction: column;
  }

  .footer-inner {
    flex-direction: column;
    text-align: center;
  }
}