/* ============================================
   Quang Anh Bui — Architecture Portfolio
   Style: Herzog & de Meuron inspired
   ============================================ */

:root {
  --black: #000;
  --white: #fff;
  --grey-light: #f5f5f5;
  --grey-mid: #999;
  --grey-dark: #333;
  --font-main: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 2rem;
  --spacing-lg: 4rem;
  --spacing-xl: 6rem;
  --max-width: 1400px;
  --nav-height: 60px;
}

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-main);
  color: var(--black);
  background: var(--white);
  line-height: 1.5;
  overflow-x: hidden;
}

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

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

ul, ol {
  list-style: none;
}

/* ---- Typography ---- */

h1, h2, h3, h4 {
  font-weight: 400;
  line-height: 1.2;
}

h1 {
  font-size: 2.5rem;
}

h2 {
  font-size: 1.75rem;
}

h3 {
  font-size: 1.125rem;
}

.text-sm {
  font-size: 0.875rem;
}

.text-xs {
  font-size: 0.75rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.text-grey {
  color: var(--grey-mid);
}

/* ---- Layout ---- */

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

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

.divider {
  border: none;
  border-top: 1px solid #e0e0e0;
  margin: var(--spacing-lg) 0;
}

/* ---- Header / Navigation ---- */

.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--white);
  border-bottom: 1px solid #e0e0e0;
  height: var(--nav-height);
  transition: transform 0.3s ease;
}

.header.hidden {
  transform: translateY(-100%);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--nav-height);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.nav__logo {
  font-size: 1.125rem;
  font-weight: 500;
  letter-spacing: -0.02em;
}

.nav__logo span {
  display: none;
}

.nav__links {
  display: flex;
  gap: var(--spacing-md);
  align-items: center;
}

.nav__links a {
  font-size: 0.875rem;
  position: relative;
  padding-bottom: 2px;
}

.nav__links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background: var(--black);
  transition: width 0.3s ease;
}

.nav__links a:hover::after,
.nav__links a.active::after {
  width: 100%;
}

.nav__menu-btn {
  display: none;
  background: none;
  border: none;
  font-family: var(--font-main);
  font-size: 0.875rem;
  cursor: pointer;
  padding: var(--spacing-xs);
}

/* Mobile menu overlay */
.menu-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--white);
  z-index: 999;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: var(--spacing-lg);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}

.menu-overlay.open {
  opacity: 1;
  pointer-events: all;
}

.menu-overlay__links {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.menu-overlay__links a {
  font-size: 2rem;
  font-weight: 300;
}

.menu-overlay__links a:hover {
  opacity: 0.5;
}

/* ---- Hero ---- */

.hero {
  padding-top: calc(var(--nav-height) + var(--spacing-xl));
  padding-bottom: var(--spacing-xl);
}

.hero__title {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 300;
  line-height: 1.15;
  max-width: 800px;
  margin-bottom: var(--spacing-md);
}

.hero__subtitle {
  font-size: 1rem;
  color: var(--grey-mid);
  font-weight: 400;
}

/* ---- Project Grid ---- */

.projects-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--spacing-md);
  padding-top: calc(var(--nav-height) + var(--spacing-lg));
}

.projects-grid--home {
  padding-top: 0;
}

.project-card {
  cursor: pointer;
  transition: opacity 0.3s ease;
}

.project-card:hover {
  opacity: 0.7;
}

.project-card__image {
  width: 100%;
  aspect-ratio: 4/3;
  background: var(--grey-light);
  margin-bottom: var(--spacing-sm);
  overflow: hidden;
  position: relative;
}

.project-card__image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.6s ease;
}

.project-card:hover .project-card__image img {
  transform: scale(1.03);
}

.project-card__number {
  font-size: 0.75rem;
  color: var(--grey-mid);
  margin-bottom: 0.25rem;
  font-variant-numeric: tabular-nums;
}

.project-card__title {
  font-size: 1rem;
  font-weight: 400;
  margin-bottom: 0.25rem;
  line-height: 1.3;
}

.project-card__meta {
  font-size: 0.8125rem;
  color: var(--grey-mid);
}

/* ---- Project Filters ---- */

.filters {
  padding-top: calc(var(--nav-height) + var(--spacing-lg));
  padding-bottom: var(--spacing-md);
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  align-items: center;
}

.filters__label {
  font-size: 0.875rem;
  color: var(--grey-mid);
  margin-right: var(--spacing-sm);
}

.filter-btn {
  background: none;
  border: 1px solid #e0e0e0;
  padding: 0.375rem 1rem;
  font-family: var(--font-main);
  font-size: 0.8125rem;
  cursor: pointer;
  transition: all 0.2s ease;
}

.filter-btn:hover,
.filter-btn.active {
  background: var(--black);
  color: var(--white);
  border-color: var(--black);
}

.projects-grid--filtered {
  padding-top: var(--spacing-md);
}

/* ---- About Page ---- */

.about {
  padding-top: calc(var(--nav-height) + var(--spacing-xl));
}

.about__intro {
  font-size: clamp(1.25rem, 3vw, 2rem);
  font-weight: 300;
  line-height: 1.4;
  max-width: 900px;
  margin-bottom: var(--spacing-xl);
}

.about__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-lg);
  align-items: start;
}

.about__portrait {
  width: 100%;
  max-width: 500px;
}

.about__portrait img {
  width: 100%;
  filter: grayscale(100%);
  transition: filter 0.5s ease;
}

.about__portrait:hover img {
  filter: grayscale(0%);
}

.about__details h3 {
  margin-bottom: var(--spacing-sm);
  font-weight: 500;
}

.about__details p {
  color: var(--grey-dark);
  margin-bottom: var(--spacing-md);
  line-height: 1.7;
}

.about__section {
  margin-bottom: var(--spacing-lg);
}

.about__section h2 {
  margin-bottom: var(--spacing-md);
  font-weight: 400;
  font-size: 1.25rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.about__list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.about__list-item {
  display: flex;
  justify-content: space-between;
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid #e0e0e0;
}

.about__list-item span:first-child {
  font-weight: 400;
}

.about__list-item span:last-child {
  color: var(--grey-mid);
  font-size: 0.875rem;
}

/* ---- Contact Page ---- */

.contact {
  padding-top: calc(var(--nav-height) + var(--spacing-xl));
  min-height: 70vh;
}

.contact__grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-lg);
}

.contact__title {
  font-size: clamp(1.5rem, 3vw, 2.5rem);
  font-weight: 300;
  margin-bottom: var(--spacing-lg);
}

.contact__block {
  margin-bottom: var(--spacing-lg);
}

.contact__block h3 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--grey-mid);
  margin-bottom: var(--spacing-sm);
}

.contact__block p,
.contact__block a {
  font-size: 1.125rem;
  line-height: 1.7;
}

.contact__block a:hover {
  opacity: 0.5;
}

/* ---- Project Detail ---- */

.project-detail {
  padding-top: calc(var(--nav-height) + var(--spacing-lg));
}

.project-detail__header {
  margin-bottom: var(--spacing-lg);
}

.project-detail__number {
  font-size: 0.875rem;
  color: var(--grey-mid);
  margin-bottom: var(--spacing-xs);
}

.project-detail__title {
  font-size: clamp(1.75rem, 4vw, 3rem);
  font-weight: 300;
  margin-bottom: var(--spacing-sm);
}

.project-detail__meta {
  display: flex;
  gap: var(--spacing-lg);
  color: var(--grey-mid);
  font-size: 0.875rem;
}

.project-detail__hero-image {
  width: 100%;
  aspect-ratio: 16/9;
  background: var(--grey-light);
  margin-bottom: var(--spacing-lg);
  overflow: hidden;
}

.project-detail__hero-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.project-detail__content {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.project-detail__sidebar h3 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--grey-mid);
  margin-bottom: var(--spacing-xs);
}

.project-detail__sidebar p {
  margin-bottom: var(--spacing-md);
}

.project-detail__description {
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--grey-dark);
}

.project-detail__gallery {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
}

.project-detail__gallery-item {
  aspect-ratio: 4/3;
  background: var(--grey-light);
  overflow: hidden;
}

.project-detail__gallery-item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.project-detail__gallery-item--full {
  grid-column: 1 / -1;
  aspect-ratio: 16/9;
}

.project-detail__nav {
  display: flex;
  justify-content: space-between;
  padding: var(--spacing-md) 0;
  border-top: 1px solid #e0e0e0;
}

.project-detail__nav a {
  font-size: 0.875rem;
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.project-detail__nav a:hover {
  opacity: 0.5;
}

/* ---- Footer ---- */

.footer {
  border-top: 1px solid #e0e0e0;
  padding: var(--spacing-lg) 0;
  margin-top: var(--spacing-xl);
}

.footer__grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--spacing-lg);
}

.footer__address {
  font-size: 0.875rem;
  line-height: 1.8;
  color: var(--grey-dark);
}

.footer__links h4 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--grey-mid);
  margin-bottom: var(--spacing-sm);
}

.footer__links a {
  display: block;
  font-size: 0.875rem;
  margin-bottom: var(--spacing-xs);
  color: var(--grey-dark);
}

.footer__links a:hover {
  color: var(--black);
}

.footer__bottom {
  margin-top: var(--spacing-lg);
  padding-top: var(--spacing-md);
  border-top: 1px solid #e0e0e0;
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--grey-mid);
}

/* ---- Page Transition ---- */

.page-content {
  animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ---- Responsive ---- */

@media (max-width: 1024px) {
  .projects-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .about__grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
  }

  .project-detail__content {
    grid-template-columns: 1fr;
  }

  .footer__grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  :root {
    --spacing-md: 1.5rem;
    --spacing-lg: 3rem;
    --spacing-xl: 4rem;
  }

  .nav__links {
    display: none;
  }

  .nav__menu-btn {
    display: block;
  }

  .projects-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }

  .contact__grid {
    grid-template-columns: 1fr;
  }

  .project-detail__gallery {
    grid-template-columns: 1fr;
  }

  .footer__grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
  }

  .footer__bottom {
    flex-direction: column;
    gap: var(--spacing-xs);
  }

  h1 {
    font-size: 1.75rem;
  }
}

@media (max-width: 480px) {
  .hero__title {
    font-size: 1.5rem;
  }

  .menu-overlay__links a {
    font-size: 1.5rem;
  }
}