/* ===== CSS CUSTOM PROPERTIES (THEME VARIABLES) ===== */
/* :root applies to the entire document */
/* Light theme is the default */
:root {
    --color-bg: #fafafa;
    --color-surface: #ffffff;
    --color-text-primary: #222222;
    --color-text-secondary: #555555;
    --color-text-muted: #777777;
    --color-text-nav: #888888;
    --color-border: #eeeeee;
    --color-border-input: #dddddd;
    --color-accent: #111111;
    --color-accent-hover: #333333;
    --color-hero-from: #f8f9ff;
    --color-hero-to: #f0f4ff;
    --color-label: #333333;
    --color-footer-text: #aaaaaa;
    --color-skill-label: #555555;
}

/* Dark theme — overrides variables when body has dark-theme class */
body.dark-theme {
    --color-bg: #121212;
    --color-surface: #1e1e1e;
    --color-text-primary: #f0f0f0;
    --color-text-secondary: #bbbbbb;
    --color-text-muted: #999999;
    --color-text-nav: #aaaaaa;
    --color-border: #333333;
    --color-border-input: #444444;
    --color-accent: #ffffff;
    --color-accent-hover: #cccccc;
    --color-hero-from: #1a1a2e;
    --color-hero-to: #16213e;
    --color-label: #cccccc;
    --color-footer-text: #666666;
    --color-skill-label: #aaaaaa;
}

/* ===== RESET & BASE ===== */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', 'Segoe UI', sans-serif;
    font-size: 16px;
    color: var(--color-text-primary);
    background-color: var(--color-bg);
    line-height: 1.7;
    transition: background-color 0.3s, color 0.3s;
}

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

ul {
    list-style: none;
}

h1,
h2,
h3 {
    margin-bottom: 1rem;
    letter-spacing: -0.02em;
}

p {
    margin-bottom: 1rem;
    color: var(--color-text-secondary);
}

/* ===== LAYOUT WRAPPER ===== */
.nav-container,
main,
footer {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 2rem;
}

main {
    padding-top: 3rem;
    padding-bottom: 5rem;
}

/* ===== HEADER & NAV ===== */
header {
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: 1.2rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background-color 0.3s, border-color 0.3s;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    color: var(--color-accent);
    font-size: 1.2rem;
    font-weight: 700;
    letter-spacing: -0.03em;
}

.nav-list {
    display: flex;
    gap: 2.5rem;
    align-items: center;
}

.nav-link {
    color: var(--color-text-nav);
    font-size: 0.95rem;
    font-weight: 500;
    padding: 0.2rem 0;
    border-bottom: 2px solid transparent;
    transition: color 0.2s, border-color 0.2s;
}

.nav-link:hover {
    color: var(--color-accent);
}

.nav-link.active {
    color: var(--color-accent);
    border-bottom: 2px solid var(--color-accent);
}

/* ===== THEME TOGGLE BUTTON ===== */
.theme-toggle {
    background: none;
    border: 1px solid var(--color-border);
    border-radius: 20px;
    padding: 0.3rem 0.8rem;
    cursor: pointer;
    font-size: 0.85rem;
    color: var(--color-text-nav);
    font-family: inherit;
    transition: all 0.2s;
}

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

/* ===== HOME ===== */
.hero {
    padding: 5rem 2rem;
    margin-bottom: 4rem;
    background: linear-gradient(135deg, var(--color-hero-from) 0%, var(--color-hero-to) 100%);
    border-radius: 16px;
    text-align: center;
    transition: background 0.3s;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 700;
    color: var(--color-accent);
    letter-spacing: -0.04em;
    line-height: 1.2;
}

.hero-subtitle {
    font-size: 1.1rem;
    color: var(--color-text-nav);
    margin-top: 0.8rem;
    font-weight: 400;
}

.about {
    max-width: 680px;
    margin: 0 auto;
    padding: 2rem 0;
}

.about h2 {
    font-size: 1.5rem;
    color: var(--color-accent);
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--color-accent);
    display: inline-block;
    margin-bottom: 1.2rem;
}

/* ===== SECTION TITLE ===== */
.projects h2,
.skills h2,
.contact h2 {
    font-size: 1.5rem;
    color: var(--color-accent);
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--color-accent);
    display: inline-block;
    margin-bottom: 2rem;
}

/* ===== PROJECTS ===== */
.project-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.project-card {
    flex: 1 1 250px;
    border: 1px solid var(--color-border);
    border-left: 4px solid var(--color-accent);
    border-radius: 8px;
    padding: 1.8rem;
    background-color: var(--color-surface);
    transition: transform 0.2s, box-shadow 0.2s, background-color 0.3s, border-color 0.3s;
}

.project-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
}

.project-card h3 {
    color: var(--color-accent);
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.project-card p {
    font-size: 0.95rem;
    color: var(--color-text-muted);
    margin-bottom: 0;
}

/* ===== SKILLS ===== */
.skills-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.skill-category {
    flex: 1 1 200px;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-top: 4px solid var(--color-accent);
    border-radius: 8px;
    padding: 1.8rem;
    transition: background-color 0.3s, border-color 0.3s;
}

.skill-category h3 {
    color: var(--color-accent);
    font-weight: 600;
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-size: 0.85rem;
}

.skill-category ul {
    list-style: none;
    padding-left: 0;
}

.skill-category li {
    margin-bottom: 0.5rem;
    color: var(--color-skill-label);
    font-size: 0.95rem;
    padding-left: 1rem;
    position: relative;
}

.skill-category li::before {
    content: '—';
    position: absolute;
    left: 0;
    color: var(--color-border);
}

/* ===== CONTACT ===== */
.contact-form {
    max-width: 560px;
}

.form-group {
    display: flex;
    flex-direction: column;
    margin-bottom: 1.5rem;
}

.form-group label {
    font-weight: 600;
    font-size: 0.9rem;
    margin-bottom: 0.4rem;
    color: var(--color-label);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.form-group input,
.form-group textarea {
    padding: 0.8rem 1rem;
    border: 1px solid var(--color-border-input);
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    background-color: var(--color-surface);
    color: var(--color-text-primary);
    transition: border-color 0.2s, background-color 0.3s, color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--color-accent);
}

button[type="submit"] {
    background-color: var(--color-accent);
    color: var(--color-bg);
    border: none;
    padding: 0.9rem 2.5rem;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
    letter-spacing: 0.02em;
}

button[type="submit"]:hover {
    background-color: var(--color-accent-hover);
    transform: translateY(-1px);
}

/* ===== FOOTER ===== */
footer {
    text-align: center;
    padding: 2rem;
    border-top: 1px solid var(--color-border);
    color: var(--color-footer-text);
    font-size: 0.85rem;
    margin-top: 3rem;
    background-color: var(--color-bg);
    transition: background-color 0.3s, border-color 0.3s;
}

/* ===== RESPONSIVE — TABLET (481px ~ 768px) ===== */
@media (min-width: 481px) and (max-width: 768px) {

    .hero h1 {
        font-size: 2.2rem;
    }

    .project-card,
    .skill-category {
        flex: 1 1 45%;
    }
}

/* ===== RESPONSIVE — MOBILE (0px ~ 480px) ===== */
@media (max-width: 480px) {

    .nav-container {
        flex-direction: column;
        gap: 0.8rem;
        text-align: center;
    }

    .nav-list {
        flex-direction: column;
        gap: 0.5rem;
        align-items: center;
    }

    .hero {
        padding: 3rem 1rem;
    }

    .hero h1 {
        font-size: 1.8rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .project-grid,
    .skills-grid {
        flex-direction: column;
    }

    .project-card,
    .skill-category {
        flex: 1 1 100%;
    }

    .contact-form {
        padding: 0;
    }
}

/* ===== PROJECT FILTER ===== */
.filter-bar {
    display: flex;
    gap: 0.8rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.filter-btn {
    background: none;
    border: 1px solid var(--color-border);
    border-radius: 20px;
    padding: 0.4rem 1.2rem;
    cursor: pointer;
    font-size: 0.9rem;
    font-family: inherit;
    color: var(--color-text-nav);
    transition: all 0.2s;
}

.filter-btn:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
}

/* Active filter button */
.filter-btn.active {
    background-color: var(--color-accent);
    border-color: var(--color-accent);
    color: var(--color-bg);
}

/* Category tag on each project card */
.category-tag {
    display: inline-block;
    margin-top: 0.8rem;
    padding: 0.2rem 0.7rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    background-color: var(--color-bg);
    color: var(--color-text-nav);
    border: 1px solid var(--color-border);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}
/* ===== GITHUB STATS PAGE ===== */
.github-section h2 {
    font-size: 1.5rem;
    color: var(--color-accent);
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--color-accent);
    display: inline-block;
    margin-bottom: 2rem;
}

.loading-text {
    color: var(--color-text-muted);
    font-size: 0.95rem;
}

.error-text {
    color: #e05555;
    font-size: 0.95rem;
}

/* Profile card */
.profile-card {
    display: flex;
    gap: 2rem;
    align-items: flex-start;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 3rem;
    transition: background-color 0.3s, border-color 0.3s;
}

.profile-avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    border: 3px solid var(--color-border);
    flex-shrink: 0;
}

.profile-info {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.profile-name {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--color-accent);
    margin-bottom: 0;
}

.profile-bio,
.profile-location {
    font-size: 0.95rem;
    color: var(--color-text-secondary);
    margin-bottom: 0;
}

/* Profile stats row */
.profile-stats {
    display: flex;
    gap: 1.5rem;
    margin-top: 0.8rem;
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.2rem;
}

.stat-number {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--color-accent);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.github-link {
    display: inline-block;
    margin-top: 0.8rem;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-accent);
    border-bottom: 1px solid var(--color-accent);
    width: fit-content;
    transition: opacity 0.2s;
}

.github-link:hover {
    opacity: 0.6;
}

/* Repos section */
.github-repos-header {
    margin-bottom: 1.5rem;
}

.github-repos-header h3 {
    font-size: 1.1rem;
    color: var(--color-accent);
}

.repos-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 1.2rem;
}

/* Repo card */
.repo-card {
    flex: 1 1 280px;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-left: 4px solid var(--color-accent);
    border-radius: 8px;
    padding: 1.4rem;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    transition: transform 0.2s, box-shadow 0.2s, background-color 0.3s;
}

.repo-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.08);
}

.repo-name {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-accent);
    word-break: break-all;
}

.repo-name:hover {
    opacity: 0.7;
}

.repo-description {
    font-size: 0.88rem;
    color: var(--color-text-muted);
    margin-bottom: 0;
    flex-grow: 1;
}

.repo-meta {
    display: flex;
    gap: 1rem;
    font-size: 0.82rem;
    color: var(--color-text-nav);
    margin-top: auto;
}