/* ===== CSS Variables / Themes ===== */
:root {
  /* Light theme (default) */
  --color-bg: #f5f5f0;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #555566;
  --color-border: #e0e0d8;
  --color-accent: #4a6741;
  --color-accent-hover: #3d5636;
  --color-tag-bg: #e8efe6;
  --color-tag-text: #3d5636;
  --color-header-bg: #ffffff;
  --color-footer-bg: #f0f0ea;
  --color-shadow: rgba(0, 0, 0, 0.08);
  --color-shadow-hover: rgba(0, 0, 0, 0.16);
  --color-card-footer: #fafaf8;
}

[data-theme="dark"] {
  --color-bg: #121218;
  --color-surface: #1e1e2a;
  --color-text: #e8e8ec;
  --color-text-secondary: #a0a0b0;
  --color-border: #2e2e3e;
  --color-accent: #7eb36a;
  --color-accent-hover: #92c580;
  --color-tag-bg: #2a3328;
  --color-tag-text: #92c580;
  --color-header-bg: #1a1a24;
  --color-footer-bg: #16161e;
  --color-shadow: rgba(0, 0, 0, 0.3);
  --color-shadow-hover: rgba(0, 0, 0, 0.5);
  --color-card-footer: #1a1a26;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Noto Sans TC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* ===== Header ===== */
.site-header {
  background-color: var(--color-header-bg);
  border-bottom: 1px solid var(--color-border);
  padding: 2rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 100;
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.site-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.site-subtitle {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  margin-top: 0.25rem;
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--color-border);
  border-radius: 12px;
  background-color: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  transition: background-color 0.2s, border-color 0.2s, transform 0.2s;
  flex-shrink: 0;
}

.theme-toggle:hover {
  transform: scale(1.05);
  border-color: var(--color-accent);
}

.theme-toggle:active {
  transform: scale(0.95);
}

/* Show/hide sun/moon icons based on theme */
.icon-moon { display: none; }
.icon-sun { display: block; }

[data-theme="dark"] .icon-moon { display: block; }
[data-theme="dark"] .icon-sun { display: none; }

/* ===== Main / Projects Grid ===== */
.projects-section {
  flex: 1;
  padding: 2.5rem 1.5rem;
  max-width: 1280px;
  margin: 0 auto;
  width: 100%;
}

.projects-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

/* ===== Project Card ===== */
.project-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  overflow: hidden;
  transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
  box-shadow: 0 2px 8px var(--color-shadow);

  /* Scroll animation initial state */
  opacity: 0;
  transform: translateY(24px);
}

.project-card.visible {
  opacity: 1;
  transform: translateY(0);
  transition: opacity 0.5s ease, transform 0.5s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

@media (hover: hover) {
  .project-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 32px var(--color-shadow-hover);
    border-color: var(--color-accent);
  }

  .project-card.visible:hover {
    transform: translateY(-8px);
  }

  .project-card:hover .card-icon img {
    transform: scale(1.1);
  }

  .project-card:hover .visit-link {
    color: var(--color-accent-hover);
  }
}

.card-link {
  display: flex;
  flex-direction: column;
  height: 100%;
  text-decoration: none;
  color: inherit;
}

.card-icon {
  width: 100%;
  padding: 2rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--color-bg);
}

.card-icon img {
  width: 64px;
  height: 64px;
  border-radius: 12px;
  transition: transform 0.4s ease;
}

.card-body {
  padding: 1.25rem 1.5rem;
  flex: 1;
}

.card-title {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--color-text);
}

.card-desc {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
  margin-bottom: 1rem;
}

/* ===== Tags ===== */
.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.25rem 0.75rem;
  border-radius: 100px;
  background-color: var(--color-tag-bg);
  color: var(--color-tag-text);
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* ===== Card Footer ===== */
.card-footer {
  padding: 0.875rem 1.5rem;
  border-top: 1px solid var(--color-border);
  background-color: var(--color-card-footer);
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

.visit-link {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-accent);
  transition: color 0.2s ease;
}

/* ===== Footer ===== */
.site-footer {
  background-color: var(--color-footer-bg);
  border-top: 1px solid var(--color-border);
  padding: 1.5rem;
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  transition: background-color 0.3s ease, border-color 0.3s ease, color 0.3s ease;
}

/* ===== Responsive Breakpoints ===== */

/* Tablet: 2 columns */
@media (min-width: 640px) {
  .projects-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Desktop: 3 columns */
@media (min-width: 960px) {
  .projects-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
  }

  .site-header {
    padding: 2.5rem 2rem;
  }

  .site-title {
    font-size: 2rem;
  }

  .projects-section {
    padding: 3rem 2rem;
  }
}

/* Large screens: 4 columns */
@media (min-width: 1280px) {
  .projects-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* Small mobile adjustments */
@media (max-width: 400px) {
  .site-title {
    font-size: 1.4rem;
  }

  .site-subtitle {
    font-size: 0.85rem;
  }

  .card-body {
    padding: 1rem 1.25rem;
  }

  .card-footer {
    padding: 0.75rem 1.25rem;
  }
}

/* ===== Accessibility ===== */
@media (prefers-reduced-motion: reduce) {
  .project-card,
  .project-card.visible,
  .card-icon img,
  .theme-toggle {
    transition: none;
  }

  .project-card {
    opacity: 1;
    transform: none;
  }
}

/* Focus styles for keyboard navigation */
.card-link:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: 16px;
}

.theme-toggle:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}