/* ========================================================
   Theme (Dark/Light) & Controls (Clean, No Emojis)
   ======================================================== */

:root {
    --bg-main: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --text-muted: #64748b;
    --card-bg: #ffffff;
    --card-border: #e2e8f0;
    --card-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
    --navbar-bg: #060e66;
    --navbar-text: #ffffff;
    --badge-highlight-yellow: #fef3c7;
    --badge-highlight-blue: #e0e7ff;
    --pub-desc-color: #00796b;
    --timeline-bg: #ffffff;
    --timeline-axis: #000000;
    --timeline-axis-label: #52606b;
    --border-divider: #e2e8f0;
}

html[data-theme="dark"],
body[data-theme="dark"] {
    --bg-main: #0b0f19;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --card-bg: #141c2e;
    --card-border: #26354f;
    --card-shadow: 0 4px 16px rgba(0, 0, 0, 0.45);
    --navbar-bg: #030712;
    --navbar-text: #f8fafc;
    --badge-highlight-yellow: #422006;
    --badge-highlight-blue: #1e1b4b;
    --pub-desc-color: #2dd4bf;
    --timeline-bg: #141c2e;
    --timeline-axis: #64748b;
    --timeline-axis-label: #94a3b8;
    --border-divider: #26334d;
}

/* Base Body & Containers */
html, body {
    background-color: var(--bg-main) !important;
    color: var(--text-primary) !important;
    transition: background-color 0.25s ease, color 0.25s ease;
}

body {
    margin-top: 72px !important;
}

#bio {
    padding-top: 15px;
}

p, span, h1, h2, h3, h4, h5, h6, li, td, th {
    color: var(--text-primary);
}

.home-section,
.home-section:nth-of-type(even) {
    background-color: var(--bg-main) !important;
}

hr {
    border-color: var(--border-divider) !important;
}

table,
table table,
table > tbody > tr > td,
table > tbody > tr > th,
table > tbody > tr:nth-child(odd) > td,
table > tbody > tr:nth-child(odd) > th,
table > tbody > tr:hover > td,
table > tbody > tr:hover > th {
    background-color: transparent !important;
    border-color: var(--border-divider) !important;
}

/* ========================================================
   Modern 1-Line Header & Navbar
   ======================================================== */
#navbar-main {
    background-color: var(--navbar-bg) !important;
    border: none;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.18);
    z-index: 1030;
    transition: background-color 0.25s ease;
    height: 56px;
    min-height: 56px;
}

#navbar-main .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
    width: 100% !important;
    max-width: 1440px !important;
    padding-left: 20px;
    padding-right: 20px;
}

#navbar-main .navbar-header {
    display: flex;
    align-items: center;
    float: none;
    margin: 0;
    flex-shrink: 0;
}

#navbar-main .navbar-brand {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 0;
    margin-right: 14px;
    height: auto;
    font-size: 17px;
    font-weight: 700;
    color: #ffffff !important;
    text-decoration: none !important;
}

#navbar-main .navbar-brand .brand-name {
    color: #ffffff;
    letter-spacing: -0.3px;
}

#navbar-main .navbar-brand .brand-divider {
    color: rgba(255, 255, 255, 0.45);
    font-weight: 400;
    margin: 0 2px;
}

#navbar-main .navbar-brand .brand-chinese {
    color: rgba(255, 255, 255, 0.9);
    font-size: 15px;
    font-weight: 500;
}

@media (min-width: 992px) {
    #navbar-main .navbar-collapse {
        padding: 0;
        border: none;
        box-shadow: none;
        display: flex !important;
        align-items: center;
        justify-content: flex-end;
        flex: 1;
        float: none;
    }

    #navbar-main .navbar-nav {
        display: flex;
        align-items: center;
        flex-direction: row;
        margin: 0;
        padding: 0;
        list-style: none;
        gap: 2px;
        float: none;
    }

    #navbar-main .navbar-nav > li {
        float: none;
        display: inline-flex;
        align-items: center;
    }
}

#navbar-main .navbar-nav > li > a {
    padding: 7px 7px;
    font-size: 13px;
    font-weight: 600;
    color: rgba(255, 255, 255, 0.88) !important;
    border-radius: 6px;
    transition: all 0.15s ease;
    white-space: nowrap;
    text-decoration: none !important;
    line-height: 1.2;
}

#navbar-main .navbar-nav > li > a:hover,
#navbar-main .navbar-nav > li > a:focus {
    color: #ffffff !important;
    background-color: rgba(255, 255, 255, 0.14) !important;
}

/* Nav Controls Box */
.nav-controls-box {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    margin-left: 10px;
    flex-shrink: 0;
}

.lang-switch-group {
    display: inline-flex;
    align-items: center;
    background: rgba(255, 255, 255, 0.14);
    border: 1px solid rgba(255, 255, 255, 0.25);
    border-radius: 20px;
    padding: 2px;
}

.lang-btn {
    background: transparent;
    border: none;
    color: rgba(255, 255, 255, 0.75);
    font-size: 11.5px;
    font-weight: 700;
    padding: 3px 8px;
    border-radius: 14px;
    cursor: pointer;
    transition: all 0.15s ease;
    line-height: 1.2;
}

.lang-btn:hover {
    color: #ffffff;
}

.lang-btn.active {
    background: #ffffff;
    color: #060e66;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.25);
}

html[data-theme="dark"] .lang-btn.active {
    background: #3b82f6;
    color: #ffffff;
}

/* Polished Theme Toggle Button */
.theme-toggle-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background: rgba(255, 255, 255, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.3);
    color: #ffffff;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.theme-toggle-btn .theme-icon {
    font-size: 13px;
    color: #facc15; /* Golden moon */
}

.theme-toggle-btn:hover {
    background: rgba(255, 255, 255, 0.26);
    border-color: rgba(255, 255, 255, 0.5);
    transform: translateY(-1px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

html[data-theme="dark"] .theme-toggle-btn {
    background: #1e293b;
    border: 1px solid #475569;
    color: #f8fafc;
}

html[data-theme="dark"] .theme-toggle-btn .theme-icon {
    color: #f59e0b; /* Golden sun */
}

html[data-theme="dark"] .theme-toggle-btn:hover {
    background: #334155;
    border-color: #64748b;
    color: #ffffff;
}

/* Medium screen compaction (1200px down to 992px) */
@media (max-width: 1220px) and (min-width: 992px) {
    #navbar-main .navbar-nav > li > a {
        padding: 6px 5px;
        font-size: 12px;
    }
    #navbar-main .navbar-brand {
        font-size: 15px;
        margin-right: 8px;
    }
    .nav-controls-box {
        gap: 5px;
        margin-left: 6px;
    }
    .theme-toggle-btn {
        padding: 4px 8px;
    }
}

/* Tablet & Mobile Collapsed Navigation (<992px) */
@media (max-width: 991px) {
    #navbar-main {
        height: auto;
    }
    #navbar-main .container {
        flex-wrap: wrap;
        padding-top: 10px;
        padding-bottom: 10px;
    }
    #navbar-main .navbar-header {
        width: 100%;
        justify-content: space-between;
    }
    #navbar-main .navbar-toggle {
        display: block !important;
        margin: 0;
        border: 1px solid rgba(255, 255, 255, 0.3);
        background: rgba(255, 255, 255, 0.1);
        border-radius: 6px;
        padding: 8px 10px;
    }
    #navbar-main .navbar-toggle .icon-bar {
        background-color: #ffffff;
    }
    #navbar-main .navbar-collapse {
        display: none !important;
        width: 100%;
        max-height: 80vh;
        overflow-y: auto;
        flex-direction: column;
        align-items: stretch;
        margin-top: 10px;
        background: var(--navbar-bg);
        border-top: 1px solid rgba(255, 255, 255, 0.15);
        padding-top: 10px;
        padding-bottom: 14px;
    }
    #navbar-main .navbar-collapse.in,
    #navbar-main .navbar-collapse.show {
        display: flex !important;
    }
    #navbar-main .navbar-nav {
        flex-direction: column;
        align-items: stretch;
        width: 100%;
        gap: 4px;
    }
    #navbar-main .navbar-nav > li > a {
        padding: 10px 14px;
        font-size: 14px;
    }
    .hidden-xs {
        display: none !important;
    }
    .mobile-nav-controls {
        display: inline-flex !important;
        align-items: center;
        gap: 8px;
    }
}

@media (min-width: 992px) {
    .visible-xs {
        display: none !important;
    }
    .mobile-nav-controls {
        display: none !important;
    }
    #navbar-main .navbar-toggle {
        display: none !important;
    }
}

/* Preloader Screen with Progress Bar */
.preloader {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: var(--bg-main);
    z-index: 99999;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: opacity 0.4s ease, visibility 0.4s ease;
}

.preloader.fade-out {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.preloader-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}

.preloader-logo {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 26px;
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.preloader-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: #2563eb;
    animation: preloader-pulse 1.2s infinite ease-in-out;
}

@keyframes preloader-pulse {
    0%, 100% { transform: scale(0.8); opacity: 0.6; }
    50% { transform: scale(1.4); opacity: 1; }
}

.preloader-bar-container {
    width: 240px;
    height: 6px;
    background: var(--card-border);
    border-radius: 999px;
    overflow: hidden;
    position: relative;
}

.preloader-bar-fill {
    width: 20%;
    height: 100%;
    background: linear-gradient(90deg, #2563eb, #7c3aed);
    border-radius: 999px;
    transition: width 0.3s ease;
    animation: bar-indeterminate 1.4s ease-in-out infinite;
}

@keyframes bar-indeterminate {
    0% { transform: translateX(-100%); width: 30%; }
    50% { transform: translateX(50%); width: 60%; }
    100% { transform: translateX(100%); width: 30%; }
}

.preloader-status {
    font-size: 13px;
    color: var(--text-muted);
    font-weight: 500;
}

/* Publication & Paper Items Layout (Thumbnails matching text height) */
.paper-entry,
.project-entry {
    display: flex;
    flex-direction: row;
    align-items: flex-start;
    gap: 22px;
    margin-left: 8%;
    margin-right: 4%;
    margin-bottom: 28px;
    padding-bottom: 20px;
    border-bottom: 1px solid var(--border-divider);
}

.paper-entry:last-child,
.project-entry:last-child {
    border-bottom: none;
}

.paper-thumb-wrapper {
    flex-shrink: 0;
    width: 130px;
    min-height: 175px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.paper-thumb-wrapper img {
    max-width: 130px;
    max-height: 180px;
    width: auto;
    height: auto;
    object-fit: contain;
    border-radius: 4px;
    border: 1px solid var(--card-border);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    background: #ffffff;
}

.paper-thumb-wrapper img:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 14px rgba(0, 0, 0, 0.16);
}

.paper-details,
.project-details {
    flex: 1;
}

.paper-details h3,
.project-details h3 {
    margin-top: 2px;
    margin-bottom: 6px;
    font-size: 1.18em;
    font-weight: 700;
    line-height: 1.35;
}

.paper-actions-row,
.project-actions-row {
    margin-top: 4px;
    margin-bottom: 6px;
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.paper-action-link {
    display: inline-flex;
    align-items: center;
    padding: 2px 8px;
    border-radius: 4px;
    border: 1px solid var(--card-border);
    background: var(--card-bg);
    color: #2563eb !important;
    font-size: 12px;
    font-weight: 600;
    text-decoration: none !important;
    transition: all 0.15s ease;
}

.paper-action-link:hover {
    background: #2563eb;
    color: #ffffff !important;
    border-color: #2563eb;
}

/* Compact project thumbnails (FitTracker & Discord Bot) */
.project-thumb-compact {
    flex-shrink: 0;
    width: 120px;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.project-thumb-compact img {
    max-width: 110px;
    max-height: 110px;
    width: auto;
    height: auto;
    object-fit: contain;
    border-radius: 12px;
    border: 1px solid var(--card-border);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    background: #ffffff;
}

.project-thumb-compact img:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 14px rgba(0, 0, 0, 0.16);
}

.project-thumb-medium {
    flex-shrink: 0;
    width: 180px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.project-thumb-medium img {
    max-width: 180px;
    max-height: 125px;
    width: auto;
    height: auto;
    object-fit: contain;
    border-radius: 6px;
    border: 1px solid var(--card-border);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    transition: transform 0.2s ease;
    background: #ffffff;
}

/* Resume Cards in Curriculums Section (Clean in Light & Dark Mode) */
.resume-card {
    border: 1px solid var(--card-border);
    border-radius: 10px;
    padding: 24px;
    background: var(--card-bg);
    box-shadow: var(--card-shadow);
    margin-bottom: 22px;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.resume-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
}

.resume-card h4 {
    color: var(--text-primary) !important;
    font-weight: 700;
    font-size: 1.15em;
    margin-top: 0;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
}

.resume-card p {
    color: var(--text-secondary) !important;
    font-size: 14px !important;
    line-height: 1.6 !important;
    margin-bottom: 18px !important;
}

/* ========================================================
   COMPREHENSIVE DARK MODE CONTRAST & LEGIBILITY
   ======================================================== */
html[data-theme="dark"] p a,
html[data-theme="dark"] a {
    color: #60a5fa !important;
}

html[data-theme="dark"] p a:hover,
html[data-theme="dark"] a:hover {
    color: #93c5fd !important;
}

html[data-theme="dark"] h1,
html[data-theme="dark"] h2,
html[data-theme="dark"] h3,
html[data-theme="dark"] h4,
html[data-theme="dark"] h5,
html[data-theme="dark"] h6,
html[data-theme="dark"] .content-title,
html[data-theme="dark"] strong,
html[data-theme="dark"] b {
    color: #f8fafc !important;
}

html[data-theme="dark"] p,
html[data-theme="dark"] span,
html[data-theme="dark"] li {
    color: #cbd5e1;
}

html[data-theme="dark"] font[color] {
    color: #2dd4bf !important;
}

html[data-theme="dark"] .pub-authors-line,
html[data-theme="dark"] .pub-authors-line span {
    color: #94a3b8 !important;
}

html[data-theme="dark"] .author-self,
html[data-theme="dark"] .author-self b {
    color: #f1f5f9 !important;
}

html[data-theme="dark"] .chenliu-headline {
    color: #f8fafc !important;
}

html[data-theme="dark"] .chenliu-subheadline,
html[data-theme="dark"] .chenliu-location {
    color: #94a3b8 !important;
}

html[data-theme="dark"] .chenliu-email {
    color: #cbd5e1 !important;
}

html[data-theme="dark"] .chenliu-link {
    color: #cbd5e1 !important;
}

html[data-theme="dark"] .chenliu-ack {
    color: #64748b !important;
}

html[data-theme="dark"] .chinese-name {
    color: #94a3b8 !important;
}

html[data-theme="dark"] .resume-card {
    background-color: #141c2e !important;
    border-color: #26354f !important;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.45) !important;
}

html[data-theme="dark"] .resume-card h4 {
    color: #f8fafc !important;
}

html[data-theme="dark"] .resume-card p {
    color: #cbd5e1 !important;
}

html[data-theme="dark"] .btn-pdf,
html[data-theme="dark"] .btn-pdf-tech,
html[data-theme="dark"] .btn-pdf-casual {
    color: #ffffff !important;
}

html[data-theme="dark"] .paper-action-link {
    background-color: #1e293b !important;
    border-color: #334155 !important;
    color: #60a5fa !important;
}

html[data-theme="dark"] .paper-action-link:hover {
    background-color: #2563eb !important;
    color: #ffffff !important;
    border-color: #2563eb !important;
}

html[data-theme="dark"] .skill-item-badge {
    background: #141c2e !important;
    border-color: #27354f !important;
    color: #f1f5f9 !important;
}

html[data-theme="dark"] .opensource-card {
    background: rgba(99, 102, 241, 0.12) !important;
    border-color: #818cf8 !important;
}

html[data-theme="dark"] .opensource-card h4 {
    color: #f8fafc !important;
}

html[data-theme="dark"] .opensource-card p {
    color: #cbd5e1 !important;
}

html[data-theme="dark"] .paper-thumb-wrapper img,
html[data-theme="dark"] .project-thumb-compact img,
html[data-theme="dark"] .project-thumb-medium img {
    border-color: #334155 !important;
    background: #0f172a !important;
}

@media screen and (max-width: 749px) {
    .paper-entry,
    .project-entry {
        flex-direction: column;
        align-items: flex-start;
        margin-left: 0;
        margin-right: 0;
        gap: 12px;
    }

    .paper-thumb-wrapper,
    .project-thumb-compact,
    .project-thumb-medium {
        width: 120px;
        min-height: auto;
    }
}