/* ========== Global Styles & Variables ========== */
:root {
  /* Color Palette */
  --color-primary: hsl(215, 30%, 25%); /* 深藍灰 (原 --primary-color) */
  --color-primary-dark: hsl(215, 30%, 18%);
  --color-primary-light: hsl(215, 30%, 35%);

  --color-secondary: hsl(210, 25%, 97%); /* 非常淺的灰藍 (原 --secondary-color) */
  --color-white: hsl(0, 0%, 100%);
  --color-black: hsl(0, 0%, 10%);

  --color-accent1: hsl(190, 70%, 50%); /* 亮青色 (原 --accent1-color) */
  --color-accent1-dark: hsl(190, 70%, 40%);
  --color-accent2: hsl(35, 80%, 60%); /* 暖橘黃 (原 --accent2-color BFA06A) */
  --color-accent2-dark: hsl(35, 80%, 50%);

  /* Text Colors */
  --text-primary: hsl(215, 20%, 25%); /* 深灰，近黑 */
  --text-secondary: hsl(215, 15%, 45%); /* 中等灰 */
  --text-light: hsl(210, 20%, 95%);
  --text-on-primary: var(--color-white);
  --text-on-accent: var(--color-primary-dark);

  /* Border & Shadow */
  --border-color: hsl(210, 20%, 88%);
  --shadow-soft: 0 4px 12px hsla(215, 20%, 0%, 0.08);
  --shadow-medium: 0 8px 20px hsla(215, 20%, 0%, 0.1);

  /* Fonts */
  --font-primary: "Montserrat", "Noto Sans TC", sans-serif; /* Headings, EN */
  --font-secondary: "Noto Sans TC", "Montserrat", sans-serif; /* Body, ZH */

  /* Layout */
  --header-height: 70px;
  --container-width: 1140px;
  --section-padding-y: 80px;
  --border-radius-sm: 4px;
  --border-radius-md: 8px;
  --border-radius-lg: 16px;
  --border-radius-pill: 50px;

  /* Transitions */
  --transition-fast: all 0.2s ease-in-out;
  --transition-normal: all 0.3s ease-in-out;

  /* REVISED Tag Specific Colors (Text and Border derived from these) */
  /* 主色調衍生 (藍/青/紫): tech, language, education */
  /* 輔助色調衍生 (橘/黃/棕): social, award */
  /* 中性/活力色 (綠): startup */

  --tag-tech-hue: 190; --tag-tech-sat: 65%; --tag-tech-light: 55%;
  --tag-social-hue: 30; --tag-social-sat: 75%; --tag-social-light: 60%;
  --tag-startup-hue: 150; --tag-startup-sat: 50%; --tag-startup-light: 55%;
  --tag-award-hue: 40; --tag-award-sat: 85%; --tag-award-light: 60%;
  --tag-language-hue: 205; --tag-language-sat: 60%; --tag-language-light: 60%;
  --tag-education-hue: 250; --tag-education-sat: 55%; --tag-education-light: 65%;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px; /* Base font size */
}

body {
  font-family: var(--font-secondary);
  color: var(--text-primary);
  line-height: 1.7;
  background-color: var(--color-secondary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-primary);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1.3;
  margin-bottom: 0.75em;
}

h1 {
  font-size: 2.8rem;
} /* Adjusted for hero */
h2 {
  font-size: 2.2rem;
} /* Section titles */
h3 {
  font-size: 1.4rem;
} /* Card titles, sub-headings */
h4 {
  font-size: 1.1rem;
} /* Card subtitles */

p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}
strong {
  font-weight: 700;
  color: var(--text-primary);
}

a {
  color: var(--color-accent1);
  text-decoration: none;
  transition: var(--transition-fast);
}
a:hover {
  color: var(--color-accent1-dark);
}

ul {
  list-style: none;
}
img {
  max-width: 100%;
  height: auto;
  display: block;
}

.container {
  max-width: var(--container-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: 20px;
  padding-right: 20px;
}

section {
  padding: var(--section-padding-y) 0;
}
.section-bg {
  background-color: var(--color-white);
}

/* Section Title Styling */
.section-title {
  text-align: center;
  margin-bottom: 50px;
}
.section-title h2 {
  margin-bottom: 0.5em;
  position: relative;
  display: inline-block;
  padding-bottom: 0.5em;
}
.section-title h2::after {
  content: "";
  position: absolute;
  display: block;
  width: 70px;
  height: 4px;
  background: var(--color-accent1);
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  border-radius: var(--border-radius-pill);
}
.section-title p {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* Buttons */
.btn {
  display: inline-flex; /* For icon alignment */
  align-items: center;
  gap: 0.5em;
  padding: 0.75em 1.8em;
  border-radius: var(--border-radius-pill);
  font-weight: 600;
  font-family: var(--font-primary);
  font-size: 0.9rem;
  text-align: center;
  cursor: pointer;
  transition: var(--transition-normal);
  border: 2px solid transparent;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  box-shadow: 0 2px 5px hsla(0, 0%, 0%, 0.1);
}
.btn i {
  font-size: 1.1em;
}

.btn-primary {
  background-color: var(--color-accent1);
  color: var(--text-on-accent);
  border-color: var(--color-accent1);
}
.btn-primary:hover {
  background-color: var(--color-accent1-dark);
  border-color: var(--color-accent1-dark);
  color: var(--text-on-accent);
  transform: translateY(-2px);
  box-shadow: 0 4px 10px hsla(0, 0%, 0%, 0.15);
}

.btn-secondary {
  background-color: var(--color-primary);
  color: var(--text-on-primary);
  border-color: var(--color-primary);
}
.btn-secondary:hover {
  background-color: var(--color-primary-light);
  border-color: var(--color-primary-light);
  color: var(--text-on-primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 10px hsla(0, 0%, 0%, 0.15);
}

.btn-outline {
  background-color: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
  box-shadow: none;
}
.btn-outline:hover {
  background-color: var(--color-primary);
  color: var(--text-on-primary);
  transform: translateY(-2px);
}
.btn-outline.btn-accent { /* Optional: outline accent button */
  color: var(--color-accent2);
  border-color: var(--color-accent2);
}
.btn-outline.btn-accent:hover {
  background-color: var(--color-accent2);
  color: var(--text-on-accent);
}


/* ========== Header ========== */
#header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  background-color: hsla(215, 30%, 25%, 0.85); /* Semi-transparent primary */
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  z-index: 1000;
  transition: var(--transition-normal);
  box-shadow: none;
}
#header.scrolled {
  background-color: var(--color-primary);
  box-shadow: 0 2px 10px hsla(215, 30%, 0%, 0.15);
}

#header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
}

.logo {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--color-white);
  font-family: var(--font-primary);
  letter-spacing: 1px;
}
.logo:hover {
  color: var(--color-accent1);
}

#navbar ul {
  display: flex;
  gap: 35px;
}
#navbar a {
  color: var(--text-light);
  font-weight: 600;
  font-size: 0.9rem;
  padding: 5px 0;
  position: relative;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
#navbar a::after {
  content: "";
  position: absolute;
  width: 0;
  height: 2px;
  bottom: -5px;
  left: 0;
  background-color: var(--color-accent1);
  transition: width 0.3s ease;
  border-radius: var(--border-radius-pill);
}
#navbar a:hover::after,
#navbar a.active::after { /* Add .active class via JS for current section */
  width: 100%;
}
#navbar a:hover {
  color: var(--color-accent1);
}

#mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--color-white);
  font-size: 1.6rem;
  cursor: pointer;
  padding: 0.5em;
  z-index: 1001; /* Above navbar content */
}

/* ========== About Section ========== */
.about-content {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 50px;
  align-items: flex-start;
}
.about-text p {
  margin-bottom: 1.5em;
}
.about-values h3 {
  margin-bottom: 1.2em;
  color: var(--color-primary);
}
.about-values ul li {
  margin-bottom: 0.8em;
  display: flex;
  align-items: center;
  color: var(--text-secondary);
  font-size: 0.95rem;
}
.icon-value {
  color: var(--color-accent2);
  margin-right: 12px;
  font-size: 1.4em;
  width: 28px;
  text-align: center;
}

/* ========== Expertise Section ========== */
.expertise-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 30px;
}
.expertise-item {
  text-align: center;
  padding: 35px 25px;
  background-color: var(--color-white);
  border-radius: var(--border-radius-md);
  border: 1px solid var(--border-color);
  transition: var(--transition-normal);
  box-shadow: var(--shadow-soft);
}
.expertise-item:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-medium);
  border-color: var(--color-accent1);
}
.expertise-item i {
  font-size: 2.8rem;
  color: var(--color-accent1);
  margin-bottom: 25px;
  transition: var(--transition-fast);
}
.expertise-item:hover i {
  transform: scale(1.1);
  color: var(--color-accent1-dark);
}
.expertise-item h3 {
  font-size: 1.3rem;
  margin-bottom: 15px;
}
.expertise-item ul li {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 8px;
}

/* ========== Card Grid (Used for Experience & Projects) ========== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 30px;
}
.card {
  background-color: var(--color-white);
  border-radius: var(--border-radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-soft);
  transition: var(--transition-normal);
  display: flex;
  flex-direction: column;
  border: 1px solid var(--border-color);
}
.card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-medium);
}
.card-img {
  width: 100%;
  height: 220px;
  object-fit: cover;
  border-bottom: 1px solid var(--border-color);
}
.card-body {
  padding: 25px;
  flex-grow: 1;
  display: flex;
  flex-direction: column;
}
.card-title {
  font-size: 1.35rem;
  margin-bottom: 0.25em;
}
.card-subtitle {
  font-size: 0.95rem;
  color: var(--color-primary);
  font-weight: 600;
  margin-bottom: 0.5em;
  font-family: var(--font-secondary);
}
.card-date {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 1em;
  font-style: italic;
}
.card-tags {
  margin-bottom: 1em;
  display: flex;
  flex-wrap: wrap;
  gap: 0.3em;
}
.card-text {
  font-size: 0.9rem;
  margin-bottom: 1.5em;
  flex-grow: 1; /* Pushes actions to bottom */
}
.card-actions {
  margin-top: auto; /* Pushes to bottom if card-text is short */
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.card-actions .btn-outline {
  padding: 0.5em 1.2em;
  font-size: 0.8rem;
}

.card-tags { /* Re-using card-tags style */
  margin-top: 0.5em;
}


/* ========== Impact Snapshot Section ========== */
#impact {
  /* No special background, uses default section bg */
}
.impact-intro {
  text-align: center;
  max-width: 700px;
  margin: -20px auto 40px auto;
  font-size: 1.05rem;
}
.chart-container {
  position: relative;
  margin: 0 auto;
  height: 400px;
  max-width: 850px;
  background-color: var(--color-white);
  padding: 25px;
  border-radius: var(--border-radius-md);
  box-shadow: var(--shadow-medium);
  border: 1px solid var(--border-color);
}

/* ========== Contact Section ========== */
#contact .section-title p { /* Center align paragraph */
  margin-left: auto;
  margin-right: auto;
}
.contact-links {
  display: flex;
  justify-content: center;
  gap: 30px;
  flex-wrap: wrap;
  margin-top: 30px;
}
.contact-link-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  padding: 15px;
  min-width: 180px;
  text-align: center;
  color: var(--text-primary);
  transition: var(--transition-normal);
}
.contact-link-item i {
  font-size: 2.2rem;
  color: var(--color-accent1);
  transition: var(--transition-fast);
}
.contact-link-item span {
  font-size: 0.95rem;
  font-weight: 500;
}
.contact-link-item:hover {
  color: var(--color-accent1);
  transform: translateY(-5px);
}
.contact-link-item:hover i {
  transform: scale(1.1);
}
.contact-link-item:nth-child(2) i { /* LinkedIn */
    color: #0A66C2; /* LinkedIn blue */
}
.contact-link-item:nth-child(2):hover { color: #0A66C2;}

.contact-link-item:nth-child(3) i { /* GitHub */
    color: #181717; /* GitHub black */
}
.contact-link-item:nth-child(3):hover { color: #181717;}


/* ========== Footer ========== */
footer {
  background-color: var(--color-primary-dark);
  color: hsla(0, 0%, 100%, 0.7);
  padding: 30px 0;
  text-align: center;
  font-size: 0.9rem;
}
.footer-social-links {
  margin-top: 10px;
}
.footer-social-links a {
  color: hsla(0, 0%, 100%, 0.7);
  margin: 0 12px;
  font-size: 1.3rem;
}
.footer-social-links a:hover {
  color: var(--color-accent1);
}

/* === Tag Styles (New System) === */
.tag {
  display: inline-block;
  padding: 0.3em 0.8em; /* Slightly increased padding for better look */
  margin: 0.2em;
  border-radius: var(--border-radius-pill);
  font-size: 0.65rem; /* Slightly smaller for more refined look */
  font-weight: 700; /* Increased weight for better readability at small size */
  line-height: 1.3;
  border: 1px solid transparent;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  transition: var(--transition-fast);
}
.tag:hover {
  transform: translateY(-1px);
  filter: brightness(1.08); /* Slightly brighter on hover */
}

.tag-tech {
  background-color: hsla(var(--tag-tech-hue), var(--tag-tech-sat), var(--tag-tech-light), 0.15);
  color: hsl(var(--tag-tech-hue), var(--tag-tech-sat), calc(var(--tag-tech-light) - 20%));
  border-color: hsla(var(--tag-tech-hue), var(--tag-tech-sat), var(--tag-tech-light), 0.3);
}
.tag-social {
  background-color: hsla(var(--tag-social-hue), var(--tag-social-sat), var(--tag-social-light), 0.15);
  color: hsl(var(--tag-social-hue), var(--tag-social-sat), calc(var(--tag-social-light) - 20%));
  border-color: hsla(var(--tag-social-hue), var(--tag-social-sat), var(--tag-social-light), 0.3);
}
.tag-startup {
  background-color: hsla(var(--tag-startup-hue), var(--tag-startup-sat), var(--tag-startup-light), 0.15);
  color: hsl(var(--tag-startup-hue), var(--tag-startup-sat), calc(var(--tag-startup-light) - 20%));
  border-color: hsla(var(--tag-startup-hue), var(--tag-startup-sat), var(--tag-startup-light), 0.3);
}
.tag-award {
  background-color: hsla(var(--tag-award-hue), var(--tag-award-sat), var(--tag-award-light), 0.2); /* Slightly more prominent bg for award */
  color: hsl(var(--tag-award-hue), var(--tag-award-sat), calc(var(--tag-award-light) - 22%));
  border-color: hsla(var(--tag-award-hue), var(--tag-award-sat), var(--tag-award-light), 0.4);
}
.tag-language {
  background-color: hsla(var(--tag-language-hue), var(--tag-language-sat), var(--tag-language-light), 0.15);
  color: hsl(var(--tag-language-hue), var(--tag-language-sat), calc(var(--tag-language-light) - 20%));
  border-color: hsla(var(--tag-language-hue), var(--tag-language-sat), var(--tag-language-light), 0.3);
}
.tag-education {
  background-color: hsla(var(--tag-education-hue), var(--tag-education-sat), var(--tag-education-light), 0.15);
  color: hsl(var(--tag-education-hue), var(--tag-education-sat), calc(var(--tag-education-light) - 20%));
  border-color: hsla(var(--tag-education-hue), var(--tag-education-sat), var(--tag-education-light), 0.3);
}


/* Animation Classes */
.fade-in {
  opacity: 0;
  transition: opacity 1s 0.2s ease-in-out; /* Delay for hero */
}
.animate-on-scroll {
  opacity: 0;
  transform: translateY(40px);
  transition: opacity 0.7s ease-out, transform 0.7s ease-out;
}
.fade-in.visible,
.animate-on-scroll.visible {
  opacity: 1;
  transform: translateY(0);
}


/* ========== Responsive Design ========== */
@media (max-width: 992px) { /* Tablets */
  :root {
    --container-width: 920px;
    --section-padding-y: 70px;
  }
  h1 { font-size: 2.6rem; }
  #hero h1 { font-size: 2.8rem; }
  h2 { font-size: 2rem; }

  .about-content {
    grid-template-columns: 1fr; /* Stack on tablet */
    gap: 40px;
  }
  .expertise-grid {
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  }
  .card-grid {
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  }
  .hero-profile-img { width: 160px; height: 160px; }
}

@media (max-width: 768px) { /* Mobile Large */
  :root {
    --header-height: 60px;
    --section-padding-y: 60px;
  }
  body { font-size: 15px; }
  h1 { font-size: 2.2rem; }
  #hero h1 { font-size: 2.5rem; }
  h2 { font-size: 1.8rem; }
  .section-title { margin-bottom: 40px; }
  .section-title h2::after { width: 60px; height: 3px; }

  #navbar {
    position: fixed; /* Changed from absolute for better behavior */
    top: 0; /* Covers full height */
    right: -100%;
    width: 80%;
    max-width: 320px;
    height: 100vh;
    background-color: var(--color-primary-dark);
    transition: right 0.35s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    padding-top: calc(var(--header-height) + 20px);
    box-shadow: -5px 0 15px hsla(215, 30%, 0%, 0.2);
    overflow-y: auto;
  }
  #navbar.active {
    right: 0;
  }
  #navbar ul {
    flex-direction: column;
    align-items: flex-start; /* Align text left */
    gap: 0;
    padding: 0 20px;
  }
  #navbar li {
    width: 100%;
  }
  #navbar a {
    display: block;
    padding: 15px 10px;
    width: 100%;
    border-bottom: 1px solid hsla(0,0%,100%,0.1);
    font-size: 1rem;
  }
  #navbar a:hover, #navbar a.active {
    color: var(--color-accent1);
    background-color: hsla(190, 70%, 50%, 0.05);
  }
  #navbar a::after { display: none; }

  #mobile-menu-toggle { display: block; }
  /* Hamburger to X animation */
  #mobile-menu-toggle .fa-bars, #mobile-menu-toggle.active .fa-xmark { display: block; }
  #mobile-menu-toggle .fa-xmark, #mobile-menu-toggle.active .fa-bars { display: none; }
  /* Ensure X-mark is pre-loaded or defined if not default */
  #mobile-menu-toggle i { transition: transform 0.3s ease; }
  #mobile-menu-toggle.active i { transform: rotate(180deg); } /* Basic rotation */


  .expertise-grid { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: 1fr; } /* Stack cards */
  .chart-container { height: 350px; padding: 20px; }
  .hero-profile-img { width: 140px; height: 140px; }
  #hero .subtitle { font-size: 1rem; }
}

@media (max-width: 576px) { /* Mobile Small */
  body { font-size: 14px; }
  h1 { font-size: 2rem; }
  #hero h1 { font-size: 2.2rem; }
  .hero-profile-img { width: 120px; height: 120px; }
  #hero .tagline { font-size: 1.2rem; }
  .btn { padding: 0.7em 1.5em; font-size: 0.85rem; }
  .card-body { padding: 20px; }
  .card-title { font-size: 1.25rem; }
  .chart-container { height: 300px; padding: 15px; }
  .contact-link-item { min-width: 150px; }
}