/* Reset & Base Styles */
:root {
    --primary-color: #4f46e5;
    --text-dark: #1f2937;
    --text-light: #6b7280;
    --bg-light: #f9fafb;
    --bg-white: #ffffff;
    --navbar-bg: rgba(255, 255, 255, 0.9);
    --border-color: rgba(0, 0, 0, 0.05);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --text-dark: #f9fafb;
    --text-light: #9ca3af;
    --bg-light: #111827;
    --bg-white: #1f2937;
    --navbar-bg: rgba(17, 24, 39, 0.9);
    --border-color: rgba(255, 255, 255, 0.1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', 'Noto Sans KR', sans-serif;
    color: var(--text-dark);
    line-height: 1.6;
    background-color: var(--bg-white);
    overflow-x: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;
}

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

ul {
    list-style: none;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Header & Navbar */
header {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    background: var(--navbar-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
}

.navbar {
    height: 80px;
    display: flex;
    align-items: center;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.logo a {
    font-size: 1.5rem;
    font-weight: 800;
    letter-spacing: -0.5px;
}

.logo span {
    color: var(--primary-color);
}

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

.nav-links > li > a {
    font-weight: 500;
    font-size: 1rem;
    color: var(--text-dark);
}

.nav-links > li > a:hover {
    color: var(--primary-color);
}

/* Theme Switch */
.theme-switch-wrapper {
    display: flex;
    align-items: center;
    margin-left: 1.5rem;
}

.theme-switch {
    display: inline-block;
    height: 30px;
    position: relative;
    width: 60px;
}

.theme-switch input {
    display: none;
}

.slider {
    background-color: #e5e7eb;
    bottom: 0;
    cursor: pointer;
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
    transition: .4s;
    display: flex;
    align-items: center;
    justify-content: space-around;
    padding: 0 5px;
}

.slider i {
    font-size: 14px;
    color: #9ca3af;
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    background-color: #fff;
    bottom: 3px;
    content: "";
    height: 24px;
    left: 4px;
    position: absolute;
    transition: .4s;
    width: 24px;
    border-radius: 50%;
    z-index: 2;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

input:checked + .slider {
    background-color: #374151;
}

input:checked + .slider:before {
    transform: translateX(28px);
}

/* Dropdown Submenu */
.dropdown {
    position: relative;
}

.dropdown-content {
    position: absolute;
    top: 100%;
    left: 0;
    background-color: var(--bg-white);
    min-width: 180px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    border-radius: 8px;
    padding: 0.5rem 0;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.dropdown:hover .dropdown-content {
    opacity: 1;
    visibility: visible;
    transform: translateY(5px);
}

.dropdown-content li a {
    display: block;
    padding: 0.8rem 1.2rem;
    font-size: 0.9rem;
    color: var(--text-light);
}

.dropdown-content li a:hover {
    background-color: var(--bg-light);
    color: var(--primary-color);
    padding-left: 1.5rem;
}

.dropbtn i {
    font-size: 0.7rem;
    margin-left: 4px;
    transition: var(--transition);
}

.dropdown:hover .dropbtn i {
    transform: rotate(180deg);
}

/* Hero Section */
.hero {
    padding: 180px 0 100px;
    background-color: var(--bg-light);
}

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

.hero-content {
    flex: 1;
}

.hero-content h1 {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    letter-spacing: -1px;
}

.hero-content h1 span {
    color: var(--primary-color);
}

.hero-content p {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 2.5rem;
    max-width: 500px;
}

.cta-buttons {
    display: flex;
    gap: 1rem;
}

.btn {
    padding: 0.8rem 1.8rem;
    border-radius: 6px;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
}

.btn-primary:hover {
    background-color: #4338ca;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(79, 70, 229, 0.4);
}

.btn-outline {
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-outline:hover {
    background-color: var(--primary-color);
    color: #fff;
}

.hero-image {
    flex: 1;
    display: flex;
    justify-content: flex-end;
}

.abstract-shape {
    width: 350px;
    height: 350px;
    background: linear-gradient(135deg, #4f46e5 0%, #a855f7 100%);
    border-radius: 30% 70% 70% 30% / 30% 30% 70% 70%;
    animation: morph 8s ease-in-out infinite;
}

@keyframes morph {
    0% { border-radius: 30% 70% 70% 30% / 30% 30% 70% 70%; }
    50% { border-radius: 50% 50% 20% 80% / 25% 80% 20% 75%; }
    100% { border-radius: 30% 70% 70% 30% / 30% 30% 70% 70%; }
}

/* About Section */
.about {
    padding: 100px 0;
}

.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 3rem;
    font-weight: 800;
}

.about-text {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.skills {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.8rem;
    margin-top: 2rem;
}

.skill-tag {
    background-color: var(--bg-light);
    padding: 0.5rem 1.2rem;
    border-radius: 50px;
    font-size: 0.9rem;
    font-weight: 500;
    border: 1px solid var(--border-color);
}

/* Footer */
footer {
    padding: 4rem 0;
    border-top: 1px solid var(--border-color);
    text-align: center;
}

footer p {
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
}

.social-links i {
    font-size: 1.5rem;
    color: var(--text-light);
}

.social-links i:hover {
    color: var(--primary-color);
}

/* Mobile Responsive */
.nav-toggle {
    display: none;
    cursor: pointer;
    font-size: 1.5rem;
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    .hero .container {
        flex-direction: column;
        text-align: center;
    }
    .hero-content h1 {
        font-size: 2.5rem;
    }
    .hero-image {
        margin-top: 3rem;
        justify-content: center;
    }
    .abstract-shape {
        width: 250px;
        height: 250px;
    }
}