/* ==========================================================================
   Simple Gray-Tone Minimalist Portfolio Stylesheet
   Concrete Specificity & Refined Micro-Interactions
   ========================================================================== */

/* 1. Design Tokens (Dark Theme Default) */
:root {
    --bg-primary: #121214;
    --bg-secondary: #1a1a1e;
    --card-bg: #1e1e24;
    --card-border: rgba(255, 255, 255, 0.08);
    --card-hover-border: rgba(255, 255, 255, 0.25);
    
    --text-primary: #f4f4f5;
    --text-secondary: #a1a1aa;
    --text-muted: #71717a;

    --accent-main: #e4e4e7;
    --accent-contrast: #09090b;

    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 18px;

    --transition: 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Light Theme Overrides */
body.light-theme {
    --bg-primary: #f8f9fa;
    --bg-secondary: #ffffff;
    --card-bg: #ffffff;
    --card-border: rgba(0, 0, 0, 0.09);
    --card-hover-border: rgba(0, 0, 0, 0.3);

    --text-primary: #18181b;
    --text-secondary: #52525b;
    --text-muted: #a1a1aa;

    --accent-main: #18181b;
    --accent-contrast: #ffffff;
}

/* 2. Global Resets & Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: 'Inter', 'Noto Sans KR', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color var(--transition), color var(--transition);
}

a {
    color: inherit;
    text-decoration: none;
    transition: color var(--transition);
}

button {
    font-family: inherit;
    border: none;
    background: none;
    cursor: pointer;
}

/* 3. Utility Layouts & Typography */
.container {
    width: 100%;
    max-width: 1140px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section {
    padding: 6rem 0;
}
.bg-card-gray {
    background-color: var(--bg-secondary);
}

.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); }
.gap-1-5 { gap: 1.5rem; }
.gap-2 { gap: 2rem; }

.section-title-wrap {
    margin-bottom: 3.5rem;
}
.subtitle {
    font-size: 0.8rem;
    font-weight: 700;
    letter-spacing: 2px;
    color: var(--text-muted);
    display: block;
    margin-bottom: 0.5rem;
    text-transform: uppercase;
}
.title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
    margin-bottom: 0.4rem;
}
.section-desc {
    font-size: 0.95rem;
    color: var(--text-muted);
}

/* Base Cards */
.card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: 2rem;
    transition: border-color var(--transition), transform var(--transition);
    position: relative;
}
.card:hover {
    border-color: var(--card-hover-border);
    transform: translateY(-2px);
}

.card-badge {
    margin-top: 1.25rem;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.775rem;
    font-weight: 600;
    color: var(--text-muted);
    border: 1px solid var(--card-border);
    padding: 0.25rem 0.6rem;
    border-radius: var(--radius-sm);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.85rem 1.75rem;
    font-size: 0.95rem;
    font-weight: 600;
    border-radius: var(--radius-sm);
    transition: all var(--transition);
}
.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
}
.btn-primary {
    background-color: var(--text-primary);
    color: var(--bg-primary);
}
.btn-primary:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}
.btn-secondary {
    background-color: transparent;
    border: 1px solid var(--card-border);
    color: var(--text-primary);
}
.btn-secondary:hover {
    border-color: var(--text-primary);
}
.btn-outline {
    border: 1px solid var(--card-border);
    color: var(--text-primary);
    font-size: 0.85rem;
}
.btn-outline:hover {
    border-color: var(--text-primary);
}
.btn-block {
    width: 100%;
}

/* 4. Navigation Header */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    padding: 1.25rem 0;
    background: rgba(18, 18, 20, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--card-border);
    transition: background var(--transition);
}
body.light-theme .navbar {
    background: rgba(248, 249, 250, 0.85);
}

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

.nav-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 800;
    font-size: 1.15rem;
    letter-spacing: 1px;
}
.logo-mark {
    width: 32px;
    height: 32px;
    background: var(--text-primary);
    color: var(--bg-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
}
.logo-dot { color: var(--text-muted); }

.nav-menu {
    display: flex;
    gap: 2rem;
}
.nav-link {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
}
.nav-link:hover, .nav-link.active {
    color: var(--text-primary);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}
.theme-toggle {
    width: 36px;
    height: 36px;
    border: 1px solid var(--card-border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.95rem;
    transition: border-color var(--transition);
}
.theme-toggle:hover {
    border-color: var(--text-primary);
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    width: 24px;
}
.hamburger span {
    width: 100%;
    height: 2px;
    background: var(--text-primary);
}

/* 5. Hero Section & Status Pill */
.hero {
    min-height: 100vh;
    padding-top: 8rem;
    padding-bottom: 5rem;
    display: flex;
    align-items: center;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.25fr 0.75fr;
    align-items: center;
    gap: 3.5rem;
}

.status-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-secondary);
    border: 1px solid var(--card-border);
    padding: 0.4rem 0.9rem;
    border-radius: 999px;
    margin-bottom: 1.5rem;
    background: rgba(255, 255, 255, 0.03);
}
.pulse-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: #10b981;
    box-shadow: 0 0 10px #10b981;
    animation: pulseGlow 2s infinite;
}
@keyframes pulseGlow {
    0% { transform: scale(0.95); opacity: 0.8; }
    50% { transform: scale(1.2); opacity: 1; }
    100% { transform: scale(0.95); opacity: 0.8; }
}

.hero-heading {
    font-size: 2.6rem;
    font-weight: 800;
    line-height: 1.25;
    letter-spacing: -1px;
    margin-bottom: 1.25rem;
}
.typing-text {
    color: var(--text-secondary);
    border-bottom: 2px solid var(--text-primary);
}

.hero-subtext {
    font-size: 1.025rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    max-width: 580px;
    line-height: 1.7;
}

.hero-actions {
    display: flex;
    gap: 1rem;
    margin-bottom: 3rem;
}

.hero-metrics {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    border-top: 1px solid var(--card-border);
    padding-top: 1.75rem;
    flex-wrap: wrap;
}
.metric-item {
    display: flex;
    flex-direction: column;
}
.metric-num {
    font-size: 1.45rem;
    font-weight: 800;
    color: var(--text-primary);
}
.metric-label {
    font-size: 0.775rem;
    color: var(--text-muted);
}
.metric-divider {
    width: 1px;
    height: 32px;
    background: var(--card-border);
}

/* Portrait Visual */
.portrait-card {
    position: relative;
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--card-border);
    background: var(--card-bg);
}
.portrait-img {
    width: 100%;
    height: auto;
    display: block;
    filter: grayscale(100%) contrast(105%);
    transition: filter var(--transition);
}
.portrait-card:hover .portrait-img {
    filter: grayscale(0%) contrast(100%);
}
.portrait-tag {
    position: absolute;
    bottom: 1.25rem;
    left: 1.25rem;
    background: rgba(18, 18, 20, 0.88);
    backdrop-filter: blur(8px);
    border: 1px solid var(--card-border);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
}
body.light-theme .portrait-tag {
    background: rgba(255, 255, 255, 0.88);
}
.tag-title {
    font-size: 0.75rem;
    font-weight: 800;
    letter-spacing: 1px;
    display: block;
}
.tag-sub {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* 6. Philosophy & Cards */
.card-num {
    font-size: 0.8rem;
    font-weight: 800;
    color: var(--text-muted);
    margin-bottom: 1rem;
}
.card-heading {
    font-size: 1.15rem;
    margin-bottom: 0.75rem;
}
.card-desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* 7. Skills Section */
.skills-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: 2rem;
}
.skill-title {
    font-size: 1.15rem;
    margin-bottom: 1.5rem;
}
.skill-item {
    margin-bottom: 1.25rem;
}
.skill-label {
    display: flex;
    justify-content: space-between;
    font-size: 0.875rem;
    font-weight: 500;
    margin-bottom: 0.4rem;
}
.skill-bar {
    width: 100%;
    height: 6px;
    background: rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-sm);
    overflow: hidden;
}
body.light-theme .skill-bar {
    background: rgba(0, 0, 0, 0.08);
}
.skill-progress {
    height: 100%;
    background: var(--text-primary);
    border-radius: var(--radius-sm);
}

.tag-cloud {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}
.tag {
    padding: 0.45rem 0.8rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--card-border);
    background: var(--bg-primary);
    font-size: 0.825rem;
    color: var(--text-secondary);
}
.tag-highlight {
    border-color: var(--text-primary);
    color: var(--text-primary);
    font-weight: 600;
}

.skill-quote {
    font-size: 0.875rem;
    color: var(--text-muted);
    font-style: italic;
    border-left: 2px solid var(--text-primary);
    padding-left: 1rem;
    margin-top: 1rem;
}

/* 8. Projects Section & Mini Metrics */
.filter-group {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2.5rem;
    flex-wrap: wrap;
}
.filter-btn {
    padding: 0.45rem 1.1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--card-border);
    color: var(--text-secondary);
    font-size: 0.85rem;
    transition: all var(--transition);
}
.filter-btn.active, .filter-btn:hover {
    background: var(--text-primary);
    color: var(--bg-primary);
    border-color: var(--text-primary);
}

.project-item {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}
.project-cat {
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--text-muted);
    text-transform: uppercase;
    margin-bottom: 0.5rem;
}
.project-heading {
    font-size: 1.15rem;
    margin-bottom: 0.5rem;
}
.project-sub {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.project-metrics-mini {
    display: flex;
    gap: 0.8rem;
    margin-bottom: 1.25rem;
    font-size: 0.775rem;
    color: var(--text-primary);
    font-weight: 600;
}
.project-metrics-mini span {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--card-border);
    padding: 0.2rem 0.5rem;
    border-radius: var(--radius-sm);
}

.project-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid var(--card-border);
    padding-top: 1rem;
}
.project-tech {
    font-size: 0.775rem;
    color: var(--text-muted);
}
.btn-link {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
}
.btn-link:hover { opacity: 0.7; }

/* 9. Contact Section & Email Copy */
.contact-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: 2rem;
}
.contact-desc {
    font-size: 0.925rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
}
.contact-list {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    margin-bottom: 2rem;
}
.contact-row {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}
.row-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
}
.row-val {
    font-size: 0.95rem;
    font-weight: 600;
}
.email-copy-wrap {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}
.copy-btn {
    font-size: 0.775rem;
    padding: 0.2rem 0.6rem;
    border: 1px solid var(--card-border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    transition: all var(--transition);
}
.copy-btn:hover {
    border-color: var(--text-primary);
    color: var(--text-primary);
}

.social-links {
    display: flex;
    gap: 1rem;
}
.social-item {
    font-size: 0.85rem;
    padding: 0.45rem 0.9rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--card-border);
    color: var(--text-secondary);
}
.social-item:hover {
    border-color: var(--text-primary);
    color: var(--text-primary);
}

.form-group {
    margin-bottom: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}
.form-group label {
    font-size: 0.825rem;
    font-weight: 600;
    color: var(--text-secondary);
}
.req { color: #ef4444; }

.form-group input, .form-group textarea {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--card-border);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.9rem;
}
.form-group input:focus, .form-group textarea:focus {
    outline: none;
    border-color: var(--text-primary);
}

/* 10. Footer */
.footer {
    padding: 2rem 0;
    border-top: 1px solid var(--card-border);
    font-size: 0.85rem;
    color: var(--text-muted);
}
.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.top-btn {
    color: var(--text-primary);
}

/* 11. Modal & Toast */
.modal {
    position: fixed;
    inset: 0;
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition);
}
.modal.active { opacity: 1; pointer-events: auto; }
.modal-backdrop {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.75);
}
.modal-box {
    position: relative;
    width: 90%;
    max-width: 600px;
    max-height: 85vh;
    overflow-y: auto;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-md);
    padding: 2.25rem;
    z-index: 2001;
}
.modal-close-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    font-size: 1.5rem;
    color: var(--text-muted);
}

.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--text-primary);
    color: var(--bg-primary);
    padding: 0.85rem 1.25rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 0.875rem;
    transform: translateY(60px);
    opacity: 0;
    transition: all var(--transition);
    z-index: 3000;
}
.toast.show { transform: translateY(0); opacity: 1; }

/* Responsive Queries */
@media (max-width: 992px) {
    .hero-grid { grid-template-columns: 1fr; text-align: center; }
    .hero-subtext { margin: 0 auto 2rem auto; }
    .hero-actions { justify-content: center; }
    .hero-metrics { justify-content: center; }
    .grid-3, .grid-2 { grid-template-columns: 1fr; }
    .portrait-card { max-width: 360px; margin: 0 auto; }
    .email-copy-wrap { justify-content: center; }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 65px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 65px);
        background: var(--bg-primary);
        flex-direction: column;
        align-items: center;
        justify-content: center;
        transition: left var(--transition);
    }
    .nav-menu.active { left: 0; }
    .hamburger { display: flex; }
    .hero-heading { font-size: 2.1rem; }
}