:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f6f7fb;
  --color-text: #1f2430;
  --color-text-muted: #5b6270;
  --color-primary: #3a5ded;
  --color-primary-dark: #2c47c2;
  --color-border: #e2e5ec;
  --color-error: #d64545;
  --max-width: 960px;
  --radius: 12px;
  --transition: 0.2s ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #14161d;
    --color-bg-alt: #1b1e28;
    --color-text: #eceef2;
    --color-text-muted: #a4a9b6;
    --color-border: #2a2e3a;
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Yu Gothic", sans-serif;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
}

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

/* Header / Nav */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

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

.logo {
  font-weight: 700;
  font-size: 1.1rem;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 28px;
  margin: 0;
  padding: 0;
}

.nav-links a {
  text-decoration: none;
  color: var(--color-text);
  font-weight: 500;
  transition: color var(--transition);
}

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

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 32px;
  height: 32px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
}

.nav-toggle span {
  display: block;
  height: 2px;
  width: 100%;
  background: var(--color-text);
  transition: transform var(--transition), opacity var(--transition);
}

.nav-toggle.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle.open span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Sections */
.section {
  padding: 80px 0;
}

.section h2 {
  font-size: 1.8rem;
  margin-bottom: 32px;
  text-align: center;
}

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

/* Profile */
.profile-section {
  text-align: center;
}

.profile-avatar {
  width: 120px;
  height: 120px;
  margin: 0 auto 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 50%;
}

.profile-section h1 {
  font-size: 2.2rem;
  margin: 0 0 8px;
}

.subtitle {
  color: var(--color-primary);
  font-weight: 600;
  margin: 0 0 24px;
}

.profile-text {
  max-width: 640px;
  margin: 0 auto;
  color: var(--color-text-muted);
}

/* Career timeline */
.timeline {
  list-style: none;
  margin: 0;
  padding: 0;
  max-width: 640px;
  margin: 0 auto;
  border-left: 2px solid var(--color-border);
}

.timeline-item {
  position: relative;
  padding: 0 0 32px 28px;
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: -7px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-primary);
}

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

.timeline-date {
  display: inline-block;
  font-size: 0.85rem;
  color: var(--color-primary);
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-item h3 {
  margin: 0 0 6px;
  font-size: 1.1rem;
}

.timeline-item p {
  margin: 0;
  color: var(--color-text-muted);
}

/* Contact */
.contact-intro {
  text-align: center;
  color: var(--color-text-muted);
  margin-bottom: 32px;
}

.contact-form {
  max-width: 480px;
  margin: 0 auto 40px;
}

.form-group {
  margin-bottom: 20px;
  display: flex;
  flex-direction: column;
}

.form-group label {
  font-weight: 600;
  margin-bottom: 6px;
  font-size: 0.9rem;
}

.form-group input,
.form-group textarea {
  font: inherit;
  padding: 12px 14px;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  background: var(--color-bg);
  color: var(--color-text);
  transition: border-color var(--transition);
  resize: vertical;
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--color-primary);
}

.form-group.invalid input,
.form-group.invalid textarea {
  border-color: var(--color-error);
}

.error-message {
  color: var(--color-error);
  font-size: 0.8rem;
  min-height: 1.2em;
  margin-top: 4px;
}

.submit-btn {
  display: block;
  width: 100%;
  padding: 14px;
  font: inherit;
  font-weight: 600;
  color: #fff;
  background: var(--color-primary);
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background var(--transition);
}

.submit-btn:hover {
  background: var(--color-primary-dark);
}

.form-status {
  text-align: center;
  min-height: 1.4em;
  font-weight: 600;
  color: var(--color-primary);
}

.social-links {
  list-style: none;
  display: flex;
  justify-content: center;
  gap: 24px;
  padding: 0;
  flex-wrap: wrap;
}

.social-links a {
  text-decoration: none;
  color: var(--color-text);
  font-weight: 600;
  padding: 8px 16px;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  transition: background var(--transition), color var(--transition);
}

.social-links a:hover {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* Footer */
.site-footer {
  text-align: center;
  padding: 24px;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--color-border);
}

/* Responsive */
@media (max-width: 768px) {
  .section {
    padding: 56px 0;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    padding: 16px 24px;
    gap: 16px;
    display: none;
  }

  .nav-links.open {
    display: flex;
  }

  .profile-section h1 {
    font-size: 1.8rem;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 16px;
  }

  .section h2 {
    font-size: 1.5rem;
  }
}