:root {
    --background-color: #f0f2f5;
    --container-background: #fff;
    --text-color: #333;
    --number-background: #4a90e2;
    --number-text: #fff;
    --button-background: #50e3c2;
    --button-text: #fff;
    --button-hover-background: #48d1b7;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

body[data-theme='dark'] {
    --background-color: #121212;
    --container-background: #1e1e1e;
    --text-color: #e0e0e0;
    --number-background: #bb86fc;
    --number-text: #121212;
    --button-background: #03dac6;
    --button-text: #121212;
    --button-hover-background: #01bfa5;
    --shadow-color: rgba(255, 255, 255, 0.1);
}

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

.container {
    text-align: center;
    background-color: var(--container-background);
    padding: 40px;
    border-radius: 15px;
    box-shadow: 0 10px 20px var(--shadow-color);
    margin: 20px;
    position: relative;
    transition: background-color 0.3s ease;
}

#theme-toggle {
    position: absolute;
    top: 15px;
    right: 15px;
    padding: 8px 12px;
    font-size: 14px;
    color: var(--button-text);
    background-color: var(--button-background);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#theme-toggle:hover {
    background-color: var(--button-hover-background);
}

h1 {
    margin-bottom: 30px;
    color: var(--text-color);
}

.input-container {
    margin-bottom: 20px;
    color: var(--text-color);
}

.sets-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
    margin-bottom: 30px;
}

.number-set {
    display: flex;
    justify-content: center;
    gap: 15px;
}

.number {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 50px;
    height: 50px;
    background-color: var(--number-background);
    color: var(--number-text);
    font-size: 24px;
    font-weight: bold;
    border-radius: 50%;
    transition: transform 0.3s ease, background-color 0.3s ease;
}

.number:hover {
    transform: scale(1.1);
}

#generate-btn {
    padding: 15px 30px;
    font-size: 18px;
    color: var(--button-text);
    background-color: var(--button-background);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

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