:root {
 /* Light theme variables */
 --bg-color: #f8f9fa;
 --text-color: #212529;
 --card-bg: #ffffff;
 --border-color: #dee2e6;
 --accent-color: #007bff;
}

[data-theme="dark"] {
 /* Dark theme variables */
 --bg-color: #121212;
 --text-color: #e0e0e0;
 --card-bg: #1e1e1e;
 --border-color: #333333;
 --accent-color: #4da3ff;
}

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

body {
 font-family: "Segoe UI", system-ui, sans-serif;
 background-color: var(--bg-color);
 color: var(--text-color);
 line-height: 1.6;
 transition: background-color 0.3s ease, color 0.3s ease;
 min-height: 100vh;
}

header {
 background-color: var(--card-bg);
 border-bottom: 1px solid var(--border-color);
 padding: 1rem 0;
 position: sticky;
 top: 0;
 z-index: 100;
}

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

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

h1 {
 font-size: 2rem;
 color: var(--accent-color);
}

.theme-toggle {
 display: flex;
 align-items: center;
 gap: 10px;
 background: var(--card-bg);
 border: 2px solid var(--border-color);
 border-radius: 50px;
 padding: 6px;
 cursor: pointer;
 transition: all 0.3s ease;
}

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

.sun, .moon {
 font-size: 1.4rem;
 transition: all 0.3s ease;
}

.toggle-track {
 width: 50px;
 height: 26px;
 background: #ccc;
 border-radius: 50px;
 position: relative;
}

.toggle-track::after {
 content: "";
 position: absolute;
 top: 3px;
 left: 3px;
 width: 20px;
 height: 20px;
 background: white;
 border-radius: 50%;
 transition: all 0.3s ease;
}

input[type="checkbox"] {
 display: none;
}

input[type="checkbox"]:checked + .toggle-track {
 background: #4da3ff;
}

input[type="checkbox"]:checked + .toggle-track::after {
 transform: translateX(24px);
}

main {
 padding: 3rem 0;
}

.hero {
 text-align: center;
 margin-bottom: 4rem;
}

.hero h2 {
 font-size: 3.5rem;
 margin-bottom: 1rem;
}

.hero p {
 font-size: 1.3rem;
 max-width: 600px;
 margin: 0 auto;
 opacity: 0.9;
}

.cards {
 display: grid;
 grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
 gap: 2rem;
}

.card {
 background-color: var(--card-bg);
 border: 1px solid var(--border-color);
 border-radius: 16px;
 padding: 2rem;
 transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
 transform: translateY(-8px);
 box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
}

.card h3 {
 margin-bottom: 1rem;
 color: var(--accent-color);
}

footer {
 text-align: center;
 padding: 2rem 0;
 border-top: 1px solid var(--border-color);
 margin-top: 4rem;
 font-size: 0.9rem;
 opacity: 0.7;
}

.status {
 font-size: 0.9rem;
 margin-top: 2rem;
 opacity: 0.8;
}