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

html {
    font-size: 16px;
}

body {
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
    color: #1f2933;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

h1 {
    color: white;
    font-size: 2.5rem;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

main {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
}

.controls {
    display: flex;
    gap: 1rem;
}

button {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

#generar {
    background-color: #48bb78;
    color: white;
}

#generar:hover {
    background-color: #38a169;
    transform: translateY(-2px);
    box-shadow: 0 6px 8px rgba(0, 0, 0, 0.15);
}

#limpiar {
    background-color: #f56565;
    color: white;
}

#limpiar:hover {
    background-color: #e53e3e;
    transform: translateY(-2px);
    box-shadow: 0 6px 8px rgba(0, 0, 0, 0.15);
}

#container {
    display: flex;
    flex-wrap: wrap;
    width: 960px;
    height: 660px;
    background-color: white;
    border: 3px solid #2d3748;
    border-radius: 8px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
}

#container div {
    border: 1px solid #e2e8f0;
    transition: background-color 0.1s ease;
}