@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@400;600&display=swap');

:root {
    --background-color: #f0f2f5;
    --text-color: #333;
    --header-color: #2c3e50;
    --main-bg: #ffffff;
    --shadow: 0 10px 20px rgba(0,0,0,0.1), 0 6px 6px rgba(0,0,0,0.15);
    --transition-speed: 0.3s;
}

[data-theme="dark"] {
    --background-color: #1a1a1a;
    --text-color: #f0f2f5;
    --header-color: #ecf0f1;
    --main-bg: #2c2c2c;
    --shadow: 0 10px 20px rgba(0,0,0,0.5), 0 6px 6px rgba(0,0,0,0.5);
}

body {
    font-family: 'Poppins', 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;
    transition: background-color var(--transition-speed), color var(--transition-speed);
    background-image: linear-gradient(45deg, rgba(0,0,0,0.02) 25%, transparent 25%),
                      linear-gradient(-45deg, rgba(0,0,0,0.02) 25%, transparent 25%),
                      linear-gradient(45deg, transparent 75%, rgba(0,0,0,0.02) 75%),
                      linear-gradient(-45deg, transparent 75%, rgba(0,0,0,0.02) 75%);
    background-size: 20px 20px;
}

header {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    margin-bottom: 2rem;
}

header h1 {
    color: var(--header-color);
    font-weight: 600;
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 1rem;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
    transition: color var(--transition-speed);
}

.theme-toggle {
    background: none;
    border: 2px solid var(--header-color);
    color: var(--header-color);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    cursor: pointer;
    font-family: 'Poppins', sans-serif;
    font-weight: 600;
    transition: all var(--transition-speed);
}

.theme-toggle:hover {
    background-color: var(--header-color);
    color: var(--main-bg);
}

main {
    background: var(--main-bg);
    padding: 2rem;
    border-radius: 15px;
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 600px;
    transition: background-color var(--transition-speed), box-shadow var(--transition-speed);
}