:root {
    --primary-color: #4a90e2;
    --secondary-color: #f5a623;
    --background-color: #f0f2f5;
    --container-bg: #ffffff;
    --text-color: #333333;
    --white: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --btn-hover: #357ABD;
    --toggle-btn-bg: #e0e0e0;
}

body.dark-mode {
    --primary-color: #64b5f6;
    --secondary-color: #ffb74d;
    --background-color: #121212;
    --container-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --shadow-color: rgba(0, 0, 0, 0.5);
    --btn-hover: #42a5f5;
    --toggle-btn-bg: #333333;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
}

#theme-btn {
    background-color: var(--toggle-btn-bg);
    border: none;
    padding: 10px;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    box-shadow: 0 2px 5px var(--shadow-color);
    transition: background-color 0.3s ease, transform 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 45px;
    height: 45px;
}

#theme-btn:hover {
    transform: scale(1.1);
}

.container {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 10px 30px var(--shadow-color);
    text-align: center;
    width: 90%;
    max-width: 500px;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

h1 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

#generate-btn {
    background-color: var(--primary-color);
    color: var(--white);
    border: none;
    padding: 1rem 2rem;
    font-size: 1rem;
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.2s ease;
    margin-bottom: 1.5rem;
}

#generate-btn:hover {
    background-color: var(--btn-hover);
}

#generate-btn:active {
    transform: scale(0.98);
}

.numbers-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.number-set {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
}

.number {
    background-color: var(--secondary-color);
    color: var(--white);
    width: 40px;
    height: 40px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    font-weight: bold;
    border-radius: 50%;
    animation: fadeIn 0.5s ease-in-out;
    box-shadow: 0 2px 4px var(--shadow-color);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: scale(0.5);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}