:root {
    --color-fondo: #0d1b2a;
    --color-azul-oscuro: #1b263b;
    --color-azul-claro: #415a77;
    --color-texto: #e0e1dd;
    --color-dorado: #ffc300;
}

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--color-fondo);
    color: var(--color-texto);
    text-align: center;
    margin: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: var(--color-azul-oscuro);
    padding: 20px 0;
    width: 100%;
    border-bottom: 2px solid var(--color-dorado);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
}

header img {
    max-height: 70px;
    width: auto;
    filter: drop-shadow(0 0 5px rgba(255, 255, 255, 0.2));
}

.container {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-dorado);
    text-shadow: 0 0 10px rgba(255, 195, 0, 0.5);
    margin-bottom: 1rem;
}

.tabs {
    display: flex;
    background-color: var(--color-azul-oscuro);
    border-radius: 50px;
    padding: 5px;
    margin-bottom: 1rem;
    box-shadow: inset 0 2px 5px rgba(0,0,0,0.3);
}

.tab-btn {
    font-family: 'Poppins', sans-serif;
    background: transparent;
    border: none;
    color: var(--color-azul-claro);
    padding: 10px 20px;
    border-radius: 50px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: background-color 0.3s, color 0.3s;
}

.tab-btn:hover {
    color: var(--color-texto);
}

.tab-btn.active {
    background-color: var(--color-dorado);
    color: var(--color-fondo);
    box-shadow: 0 0 10px rgba(255, 195, 0, 0.5);
}

.subtitle {
    font-size: 1rem;
    color: var(--color-azul-claro);
    margin-top: 0;
    margin-bottom: 2.5rem;
    max-width: 450px;
    min-height: 40px; 
    display: flex;
    align-items: center;
    justify-content: center;
}

.number-container {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 2.5rem;
    perspective: 1000px; 
}

.number-box {
    width: 60px;
    height: 80px;
    background: var(--color-azul-oscuro);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 2rem;
    font-weight: 600;
    border-radius: 10px;
    box-shadow: inset 0 0 10px rgba(0,0,0,0.5);
    transition: transform 0.6s, background-color 0.6s;
    transform-style: preserve-3d;
}

.number-box span {
    display: block; 
    transform: rotateY(0deg);
    transition: transform 0.6s;
    backface-visibility: hidden;
}

.number-box.reveal {
    transform: rotateY(180deg);
    background-color: var(--color-dorado);
    color: var(--color-fondo);
}

.number-box.reveal span {
    transform: rotateY(-180deg); 
}

#generate-btn {
    background-color: var(--color-dorado);
    color: var(--color-fondo);
    border: none;
    padding: 15px 30px;
    font-size: 1.2rem;
    font-weight: 600;
    font-family: 'Poppins', sans-serif;
    border-radius: 50px;
    cursor: pointer;
    transition: transform 0.2s ease-out, box-shadow 0.2s ease-out;
    box-shadow: 0 4px 15px rgba(255, 195, 0, 0.3);
}

#generate-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(255, 195, 0, 0.5);
}

#generate-btn:active {
    transform: translateY(0);
}

footer {
    padding: 15px;
    background-color: var(--color-azul-oscuro);
    font-size: 0.8rem;
    color: var(--color-azul-claro);
    width: 100%;
}