:root {
    --primary-color: #4a90e2;
    --background-color: #f0f2f5;
    --text-color: #333;
    --white: #fff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --toggle-bg: #ddd;
    --toggle-knob: #fff;
}

[data-theme="dark"] {
    --primary-color: #5a9ff2;
    --background-color: #1a1a2e;
    --text-color: #e0e0e0;
    --white: #16213e;
    --shadow-color: rgba(0, 0, 0, 0.4);
    --toggle-bg: #5a9ff2;
    --toggle-knob: #1a1a2e;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    box-sizing: border-box;
    background-image: linear-gradient(rgba(255, 255, 255, 0.95), rgba(255, 255, 255, 0.95)), url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%239C92AC' fill-opacity='0.1'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    transition: background-color 0.3s, color 0.3s;
}

[data-theme="dark"] body {
    background-image: none;
}

.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
    z-index: 100;
}

.theme-toggle span {
    font-size: 1.2rem;
}

.toggle-switch {
    width: 56px;
    height: 28px;
    background-color: var(--toggle-bg);
    border-radius: 14px;
    border: none;
    cursor: pointer;
    position: relative;
    transition: background-color 0.3s;
    padding: 0;
}

.toggle-switch::after {
    content: '';
    position: absolute;
    top: 3px;
    left: 3px;
    width: 22px;
    height: 22px;
    background-color: var(--toggle-knob);
    border-radius: 50%;
    transition: transform 0.3s;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

[data-theme="dark"] .toggle-switch::after {
    transform: translateX(28px);
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    text-shadow: 1px 1px 2px var(--shadow-color);
}