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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 15px;
  line-height: 1.7;
  color: #1a1a1a;
  background: #ffffff;
}

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

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

/* === Typography === */
h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: 1.5rem;
}

h2 {
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
  color: #1a1a1a;
}

h3 {
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 0.5rem;
}

p {
  margin-bottom: 1.1rem;
  color: #2a2a2a;
}

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

/* === Layout === */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* === Navigation === */
nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: #ffffff;
  border-bottom: 1px solid #e8e8e8;
}

.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  font-size: 1.5rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  color: #1a1a1a;
}

.nav-brand:hover {
  color: #555;
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.nav-links a {
  font-size: 0.95rem;
  font-weight: 400;
  letter-spacing: 0.01em;
  color: #444;
  transition: color 0.15s;
}

.nav-links a:hover,
.nav-links a.active {
  color: #1a1a1a;
}

/* === Home Page === */
.home-hero {
  padding: 5rem 0 4rem;
}

.home-hero .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: start;
}

.hero-image img {
  width: 100%;
  height: auto;
  object-fit: cover;
}

.hero-text {
  border-top: 1px solid #1a1a1a;
  padding-top: 1.5rem;
}

.hero-text h1 {
  font-size: 2.2rem;
  margin-bottom: 1.8rem;
}

/* === Page Header === */
.page-header {
  padding: 3.5rem 0 1.5rem;
  border-bottom: 1px solid #e8e8e8;
  margin-bottom: 3rem;
}

.page-header h1 {
  font-size: 1rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #888;
  margin-bottom: 0;
}

/* === Research Page === */
.research-list {
  padding-bottom: 5rem;
}

.research-item {
  padding: 2.5rem 0;
  border-bottom: 1px solid #e8e8e8;
}

.research-item:first-child {
  padding-top: 0;
}

.research-item h3 a {
  color: #1a1a1a;
  text-decoration: underline;
  text-decoration-color: #ccc;
  text-underline-offset: 3px;
  transition: text-decoration-color 0.15s;
}

.research-item h3 a:hover {
  text-decoration-color: #1a1a1a;
}

.research-status {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: #888;
  margin-bottom: 0.6rem;
}

.research-item p {
  font-size: 0.97rem;
  color: #444;
  margin-top: 0.7rem;
}

/* === Data Science Page === */
.ds-grid {
  padding-bottom: 5rem;
}

.ds-section {
  padding: 2.5rem 0;
  border-bottom: 1px solid #e8e8e8;
}

.ds-section:first-child {
  padding-top: 0;
}

.ds-section p {
  font-size: 0.97rem;
  color: #444;
}

.ds-section .ds-link {
  display: inline-block;
  margin-top: 0.8rem;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: #1a1a1a;
  border-bottom: 1px solid #1a1a1a;
  padding-bottom: 1px;
  transition: opacity 0.15s;
}

.ds-section .ds-link:hover {
  opacity: 0.55;
}

.ds-section img {
  display: block;
  width: 75%;
  height: auto;
  margin: 1.2rem auto;
}

.ds-embed {
  width: 100%;
  height: 620px;
  border: none;
  margin: 1.2rem 0;
  display: block;
}

/* === Contact Section === */
.contact-section {
  padding: 2.5rem 0 5rem;
}

.contact-section p {
  color: #444;
}

.contact-section a {
  color: #1a1a1a;
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* === Footer === */
footer {
  border-top: 1px solid #e8e8e8;
  padding: 1.5rem 0;
  text-align: center;
  font-size: 0.8rem;
  color: #aaa;
  letter-spacing: 0.02em;
}

/* === Responsive === */
@media (max-width: 768px) {
  .home-hero {
    padding: 3rem 0 2.5rem;
  }

  .home-hero .container {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .hero-image {
    order: -1;
  }

  .hero-text h1 {
    font-size: 1.7rem;
  }

  .nav-links {
    gap: 1.2rem;
  }

  .nav-links a {
    font-size: 0.8rem;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 1.2rem;
  }

  .nav-inner {
    padding: 0 1.2rem;
  }
}