.opacity {
    opacity: 0;
    transition: all .5;
}

.awelcome {
    animation: welcome linear .5s;
}

.aarriba {
    animation: arriba linear .5s;
}

.aabajo {
    animation: abajo linear .5s;
}

.aderecha {
    animation: derecha linear .5s;
}

.aizquierda {
    animation: izquierda linear .5s;
}

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

@keyframes arriba {
    from {
        opacity: 0;
        transform: translateY(100px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes abajo {
    from {
        opacity: 0;
        transform: translateY(-100px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes izquierda {
    from {
        opacity: 0;
        transform: translateX(-100px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes derecha {
    from {
        opacity: 0;
        transform: translateX(100px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}