@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@400;600;700&display=swap');

:root {
    --background-color: #f0f2f5;
    --card-background: #ffffff;
    --primary-text-color: #333;
    --accent-color: #007bff;
    --accent-hover-color: #0056b3;
    --number-bg: #f8f9fa;
    --number-border: #dee2e6;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Poppins', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: var(--background-color);
    color: var(--primary-text-color);
    text-align: center;
}

.container {
    background: var(--card-background);
    padding: 2.5rem 3rem;
    border-radius: 15px;
    box-shadow: 0 10px 30px var(--shadow-color);
    width: 90%;
    max-width: 500px;
    transition: transform 0.3s ease;
}

.container:hover {
    transform: translateY(-5px);
}

h1 {
    font-size: 2.2rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--primary-text-color);
}

#numberContainer {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin: 2rem 0;
    flex-wrap: wrap;
    min-height: 60px; /* Reserve space */
}

.number {
    background-color: var(--number-bg);
    border: 1px solid var(--number-border);
    color: var(--primary-text-color);
    width: 55px;
    height: 55px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    font-weight: 600;
    border-radius: 50%;
    opacity: 0;
    transform: scale(0.8) translateY(20px);
    animation: reveal 0.5s forwards ease-out;
}

@keyframes reveal {
    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

#generateBtn {
    background: linear-gradient(45deg, var(--accent-color), var(--accent-hover-color));
    color: white;
    font-size: 1.1rem;
    font-weight: 600;
    padding: 1rem 2.5rem;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    box-shadow: 0 4px 15px rgba(0, 123, 255, 0.2);
}

#generateBtn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0, 123, 255, 0.3);
}

#generateBtn:active {
    transform: translateY(-1px);
}

/* Responsive Design */
@media (max-width: 480px) {
    .container {
        padding: 2rem 1.5rem;
    }

    h1 {
        font-size: 1.8rem;
    }

    .number {
        width: 50px;
        height: 50px;
        font-size: 1.3rem;
    }
}