:root {
    --dark-navy: #020c1b;
    --navy: #0a192f;
    --light-navy: #112240;
    --lightest-navy: #233554;
    --navy-shadow: rgba(2, 12, 27, 0.7);
    --dark-slate: #495670;
    --slate: #8892b0;
    --light-slate: #a8b2d1;
    --lightest-slate: #ccd6f6;
    --white: #e6f1ff;
    --green: #64ffda;
    --green-tint: rgba(100, 255, 218, 0.1);

    --font-mono: 'Fira Code', monospace;
    --font-sans: 'Noto Sans KR', 'Calibre', 'San Francisco', sans-serif;
    
    --fz-xxs: 12px;
    --fz-xs: 13px;
    --fz-sm: 14px;
    --fz-md: 16px;
    --fz-lg: 18px;
    --fz-xl: 20px;
    --fz-xxl: 22px;
    --fz-heading: 32px;

    --border-radius: 4px;
    --nav-height: 100px;
    --nav-scroll-height: 70px;
    --tab-height: 42px;
    --tab-width: 120px;
}

/* Reset & Global */
html {
    scroll-behavior: smooth;
    box-sizing: border-box;
    width: 100%;
}

*, *:before, *:after {
    box-sizing: inherit;
}

body {
    margin: 0;
    width: 100%;
    min-height: 100%;
    overflow-x: hidden;
    background-color: var(--navy);
    color: var(--slate);
    font-family: var(--font-sans);
    font-size: var(--fz-xl);
    line-height: 1.3;
}

a {
    display: inline-block;
    text-decoration: none;
    text-decoration-skip-ink: auto;
    color: inherit;
    position: relative;
    transition: color 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
}

a:hover {
    color: var(--green);
}

ul, ol {
    padding: 0;
    margin: 0;
    list-style: none;
}

section {
    margin: 0 auto;
    padding: 100px 0;
    max-width: 1000px;
}

.fill-height {
    min-height: 100vh;
    padding: 0; 
}

/* Typography Helpers */
.big-heading {
    margin: 0;
    font-size: clamp(40px, 8vw, 80px);
    font-weight: 600;
    color: var(--lightest-slate);
    line-height: 1.1;
}

.slate-text {
    color: var(--slate);
}

.accent-text {
    color: var(--green);
}

.numbered-heading {
    display: flex;
    align-items: center;
    position: relative;
    margin: 10px 0 40px;
    width: 100%;
    font-size: clamp(26px, 5vw, 32px);
    white-space: nowrap;
    color: var(--lightest-slate);
}

.numbered-heading::before {
    position: relative;
    bottom: 4px;
    counter-increment: section;
    content: "0" counter(section) ".";
    margin-right: 10px;
    color: var(--green);
    font-family: var(--font-mono);
    font-size: clamp(16px, 3vw, 20px);
    font-weight: 400;
}

.numbered-heading::after {
    content: "";
    display: block;
    position: relative;
    top: -5px;
    width: 300px;
    height: 1px;
    margin-left: 20px;
    background-color: var(--lightest-navy);
}

/* Navigation */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: fixed;
    top: 0;
    z-index: 11;
    padding: 0px 50px;
    width: 100%;
    height: var(--nav-height);
    background-color: rgba(10, 25, 47, 0.85);
    backdrop-filter: blur(10px);
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    counter-reset: section; /* Start counting sections */
}

.logo {
    color: var(--green);
    font-family: var(--font-mono);
    font-size: 24px;
    font-weight: 700;
    border: 2px solid var(--green);
    padding: 5px 10px;
    border-radius: 5px;
}

.nav-links {
    display: flex;
    align-items: center;
}

.nav-links ol {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0;
    margin: 0;
    list-style: none;
}

.nav-links ol li {
    margin: 0 5px;
    position: relative;
    font-size: var(--fz-xs);
}

.nav-links a {
    padding: 10px;
    font-family: var(--font-mono);
}

.nav-num {
    color: var(--green);
    margin-right: 5px;
}

.resume-api {
    color: var(--green);
    background-color: transparent;
    border: 1px solid var(--green);
    border-radius: var(--border-radius);
    padding: 0.75rem 1rem;
    font-family: var(--font-mono);
    line-height: 1;
    text-decoration: none;
    margin-left: 15px;
    font-size: var(--fz-xs);
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
}

.resume-api:hover {
    background-color: var(--green-tint);
}

/* Sidebars */
.email-sidebar-left, .email-sidebar-right {
    width: 40px;
    position: fixed;
    bottom: 0;
    left: auto;
    right: 40px;
    z-index: 10;
    color: var(--light-slate);
}

.email-sidebar-left {
    left: 40px;
    right: auto;
}

.vertical-line {
    display: block;
    width: 1px;
    height: 90px;
    margin: 0 auto;
    background-color: var(--light-slate);
}

.social-list {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin: 0;
    padding: 0;
    list-style: none;
}

.social-list li a {
    padding: 10px;
    font-size: 20px;
    transition: transform 0.2s;
}

.social-list li a:hover {
    color: var(--green);
    transform: translateY(-3px);
}

.email-link {
    margin: 20px auto;
    padding: 10px;
    font-family: var(--font-mono);
    font-size: var(--fz-xs);
    letter-spacing: 0.1em;
    writing-mode: vertical-rl;
}

/* Main Content Wrapper */
#content {
    padding: 0px 150px;
}

/* Hero Section */
.hero-section {
    display: flex;
    justify-content: center;
    flex-direction: column;
    align-items: flex-start;
    min-height: 100vh;
    padding: 0;
}

.hi-text {
    margin: 0 0 30px 4px;
    color: var(--green);
    font-family: var(--font-mono);
    font-size: clamp(var(--fz-sm), 5vw, var(--fz-md));
    font-weight: 400;
}

.hero-desc {
    margin: 20px 0 0;
    max-width: 540px;
    font-size: var(--fz-lg);
    color: var(--slate);
}

.cta-button {
    color: var(--green);
    background-color: transparent;
    border: 1px solid var(--green);
    border-radius: var(--border-radius);
    padding: 1.25rem 1.75rem;
    font-size: var(--fz-sm);
    font-family: var(--font-mono);
    line-height: 1;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    margin-top: 50px;
}

.cta-button:hover {
    background-color: var(--green-tint);
}

/* About Section */
.about-content {
    display: grid;
    grid-template-columns: 3fr 2fr;
    gap: 50px;
}

.about-text p {
    margin: 0 0 15px 0;
}

.skills-list {
    display: grid;
    grid-template-columns: minmax(140px, 200px) minmax(140px, 200px);
    gap: 0 10px;
    padding: 0;
    margin: 20px 0 0 0;
    overflow: hidden;
    list-style: none;
}

.skills-list li {
    position: relative;
    margin-bottom: 10px;
    padding-left: 20px;
    font-family: var(--font-mono);
    font-size: var(--fz-xs);
}

.skills-list li::before {
    content: "▹";
    position: absolute;
    left: 0;
    color: var(--green);
}

.about-img {
    position: relative;
    max-width: 300px;
    margin: 0 auto; /* Center on mobile / constrained areas */
}

.img-wrapper {
    display: block;
    position: relative;
    width: 100%;
    /* aspect-ratio: 1 / 1; Removed to show full image */
    border-radius: var(--border-radius);
    background-color: transparent; /* Removed tint */
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
}

.profile-pic {
    width: 100%;
    height: auto; /* Allow natural height */
    border-radius: var(--border-radius);
    position: relative;
    mix-blend-mode: normal; /* Removed multiply */
    filter: none; /* Removed grayscale */
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    display: block;
}

.img-wrapper:hover {
    background-color: transparent; /* Remove tint bg on hover */
    transform: translate(-3px, -3px); /* Move top-left slightly */
}

.img-wrapper:hover .profile-pic {
    filter: none;
    mix-blend-mode: normal;
}

/* The Frame - Aligned with Image */
.img-wrapper::after {
    content: "";
    display: block;
    position: absolute;
    width: 100%;
    height: 100%;
    border-radius: var(--border-radius);
    border: 2px solid var(--green);
    top: 0;
    left: 0;
    z-index: 1; /* Place on top of image to be visible */
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    pointer-events: none; /* Let clicks pass through to image */
}

/* Hover Effect - Optional: subtle expansion or glow instead of offset movement */
.img-wrapper:hover::after {
    top: -5px;
    left: -5px;
    width: calc(100% + 10px);
    height: calc(100% + 10px);
}

/* Experience Section (Vertical Tabs) */
.jobs-tabs {
    display: flex;
    min-height: 340px;
}

.tabs-list {
    display: flex;
    flex-direction: column;
    position: relative;
    z-index: 3;
    width: max-content;
    padding: 0;
    margin: 0;
    list-style: none;
    border-left: 2px solid var(--lightest-navy);
}

.tab-button {
    display: flex;
    align-items: center;
    width: 100%;
    height: var(--tab-height);
    padding: 0 20px 2px;
    border: 0;
    border-left: 2px solid transparent; /* Highlight line container */
    background-color: transparent;
    color: var(--slate);
    font-family: var(--font-mono);
    font-size: var(--fz-xs);
    text-align: left;
    white-space: nowrap;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    margin-left: -2px; /* Pull back to overlap border */
}

.tab-button:hover, .tab-button:focus {
    background-color: var(--light-navy);
    color: var(--green);
}

.tab-button.active {
    color: var(--green);
    border-left: 2px solid var(--green);
    background-color: var(--light-navy);
}

.tab-content-container {
    position: relative;
    width: 100%;
    margin-left: 20px;
}

.tab-panel {
    display: none;
    width: 100%;
    height: auto;
    padding: 10px 5px;
}

.tab-panel.active {
    display: block;
    animation: fadeIn 0.5s;
}

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

.job-title {
    margin-bottom: 2px;
    font-size: var(--fz-xxl);
    font-weight: 500;
    color: var(--lightest-slate);
}

.company {
    color: var(--green);
}

.job-range {
    margin-bottom: 25px;
    color: var(--light-slate);
    font-family: var(--font-mono);
    font-size: var(--fz-xs);
}

.job-desc ul {
    list-style: none;
    padding: 0;
}

.job-desc li {
    position: relative;
    padding-left: 30px;
    margin-bottom: 10px;
    font-size: var(--fz-lg);
}

.job-desc li::before {
    content: "▹";
    position: absolute;
    left: 0;
    color: var(--green);
}

/* Projects Section */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 15px;
    position: relative;
    margin-top: 50px;
}

.project-card {
    background-color: var(--light-navy);
    padding: 2rem 1.75rem;
    border-radius: var(--border-radius);
    transition: transform 0.25s cubic-bezier(0.645, 0.045, 0.355, 1);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    height: 100%;
}

.project-card:hover {
    transform: translateY(-7px);
}

.project-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 35px;
}

.folder-icon {
    color: var(--green);
    font-size: 40px;
}

.project-links a {
    color: var(--light-slate);
    margin-left: 10px;
}

.project-links a:hover {
    color: var(--green);
}

.project-title {
    color: var(--lightest-slate);
    font-size: var(--fz-xl);
    margin: 0 0 10px;
}

.project-description {
    color: var(--light-slate);
    font-size: var(--fz-md);
}

.project-tech-list {
    display: flex;
    align-items: flex-end;
    flex-grow: 1;
    flex-wrap: wrap;
    padding: 0;
    margin: 20px 0 0;
    list-style: none;
}

.project-tech-list li {
    font-family: var(--font-mono);
    font-size: var(--fz-xxs);
    line-height: 1.75;
    margin-right: 15px;
    color: var(--slate);
}

/* Education Section */
.edu-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.edu-column h3 {
    color: var(--lightest-slate);
    font-size: var(--fz-xl);
    margin-bottom: 20px;
}

.fancy-list li {
    position: relative;
    padding-left: 20px;
    margin-bottom: 15px;
    font-size: var(--fz-lg);
}

.fancy-list li::before {
    content: "▹";
    position: absolute;
    left: 0;
    color: var(--green);
}

.sub-text {
    display: block;
    font-size: var(--fz-sm);
    color: var(--slate);
    margin-top: 5px;
    font-family: var(--font-mono);
}

.lectures-wrapper {
    margin-top: 50px;
    padding: 20px;
    border: 1px solid var(--lightest-navy);
    border-radius: var(--border-radius);
    text-align: center;
}

.lectures-wrapper h3 {
    margin-bottom: 15px;
    color: var(--green);
    font-size: var(--fz-xl);
}

.lecture-tags {
    color: var(--light-slate);
    line-height: 1.8;
}

/* Footer */
.footer {
    padding: 20px;
    text-align: center;
    font-family: var(--font-mono);
    font-size: var(--fz-xxs);
    color: var(--slate);
}
.b-brand {
    color: var(--green);
}

.social-links-mobile {
    display: none; /* Hidden on desktop */
    margin-bottom: 20px;
}
.social-links-mobile ul {
    display: flex;
    justify-content: center;
}
.social-links-mobile li {
    margin: 0 10px;
}
.social-links-mobile a {
    color: var(--light-slate);
    font-size: 20px;
}

/* Responsive */
@media (max-width: 1080px) {
    #content { padding: 0 100px; }
    .email-sidebar-left, .email-sidebar-right { display: none; }
    .social-links-mobile { display: block; }
}

@media (max-width: 768px) {
    #content { padding: 0 50px; }
    .nav-links { display: none; } /* Simplified mobile nav for now */
    
    .jobs-tabs {
        display: block;
    }
    .tabs-list {
        flex-direction: row;
        width: 100%;
        overflow-x: auto;
        border-left: 0;
        border-bottom: 2px solid var(--lightest-navy);
        margin-bottom: 30px;
    }
    .tab-button {
        border-left: 0;
        border-bottom: 2px solid transparent;
        justify-content: center;
        width: auto;
        min-width: 120px;
        margin-left: 0;
    }
    .tab-button.active {
        border-left: 0;
        border-bottom: 2px solid var(--green);
        background: transparent;
        color: var(--green);
    }
    .tab-content-container { margin-left: 0; }
    
    .about-content {
        grid-template-columns: 1fr;
    }
    .about-img {
        margin: 50px auto 0;
    }

    .edu-container {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    #content { padding: 0 25px; }
    .navbar { padding: 0 25px; }
    .big-heading { font-size: 32px; }
}

.lecture-list-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 25px;
    list-style: none;
    padding: 20px 0 0;
    text-align: left;
}

.lecture-list-grid li {
    position: relative;
    padding-left: 20px;
}

.lecture-list-grid li::before {
    content: '▹';
    position: absolute;
    left: 0;
    color: var(--green);
    font-size: var(--fz-lg);
    line-height: 1.2;
}

.lectures-wrapper {
    margin-top: 50px;
    padding: 30px;
    border: 1px solid var(--lightest-navy);
    border-radius: var(--border-radius);
    text-align: left; /* Changed from center */
}

.lecture-list-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 25px;
    list-style: none;
    padding: 20px 0 0;
    text-align: left;
}

.lecture-list-grid li {
    position: relative;
    padding-left: 20px;
}

.lecture-list-grid li::before {
    content: '';
    position: absolute;
    left: 0;
    color: var(--green);
    font-size: var(--fz-lg);
    line-height: 1.2;
}