:root {
    --bg-color: #f4f4f4;
    --text-color: #333;
    --container-bg: #fff;
    --primary-color: #ff6b6b;
    --secondary-color: #777;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #f4f4f4;
    --container-bg: #2d2d2d;
    --primary-color: #ff8787;
    --secondary-color: #aaa;
    --shadow: 0 4px 6px rgba(255, 255, 255, 0.05);
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Arial', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    text-align: center;
    width: 300px;
    transition: background-color 0.3s, box-shadow 0.3s;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 1.5rem;
    margin: 0;
}

.btn-theme {
    background: none;
    border: 1px solid var(--secondary-color);
    color: var(--text-color);
    padding: 0.3rem 0.6rem;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.8rem;
}

.result-area {
    margin-bottom: 2rem;
    min-height: 3rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    font-weight: bold;
    border: 2px dashed var(--secondary-color);
    border-radius: 8px;
    padding: 1rem;
}

.button-group {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

button {
    padding: 0.8rem 1.2rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-weight: bold;
    transition: transform 0.1s;
}

button:active {
    transform: scale(0.95);
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
    flex: 2;
}

.btn-secondary {
    background-color: var(--secondary-color);
    color: #fff;
    flex: 1;
}