:root {
    --primary-color: #4a90e2;
    --secondary-color: #50e3c2;
    --background-color: #f5f7fa;
    --card-background: #ffffff;
    --text-color: #333333;
    --text-muted: #7f8c8d;
    --border-color: #e1e8ed;
    --success-color: #2ecc71;
    --error-color: #e74c3c;
    --transition: 0.3s ease;
}

[data-theme="dark"] {
    --primary-color: #5dade2;
    --secondary-color: #48c9b0;
    --background-color: #1a1a1a;
    --card-background: #2c3e50;
    --text-color: #ecf0f1;
    --text-muted: #bdc3c7;
    --border-color: #34495e;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color var(--transition), color var(--transition);
}

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

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    background-color: var(--card-background);
    padding: 1rem 0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    margin-bottom: 2rem;
}

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

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

.nav-links {
    list-style: none;
    display: flex;
    gap: 1.5rem;
}

.nav-links li a {
    color: var(--text-color);
    font-weight: 500;
}

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

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: background-color var(--transition), transform 0.1s;
}

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

.btn-primary:hover {
    background-color: #357abd;
}

.btn:active {
    transform: scale(0.98);
}

/* Forms */
.form-group {
    margin-bottom: 1.5rem;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

input[type="text"],
input[type="password"],
input[type="email"] {
    width: 100%;
    padding: 0.8rem;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--card-background);
    color: var(--text-color);
    font-size: 1rem;
}

input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(74, 144, 226, 0.2);
}

/* Cards */
.card {
    background-color: var(--card-background);
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

/* Utilities */
.text-center {
    text-align: center;
}

.mt-4 {
    margin-top: 1.5rem;
}

.mb-4 {
    margin-bottom: 1.5rem;
}

/* Theme Toggle */
.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-color);
    font-size: 1.2rem;
}

/* Responsive Header */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }

    .nav-links li {
        text-align: center;
    }
}