#cuerpo {width: 99%;
        background: #33FFFF;
        font-size: 23px;
        height:900px;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 300px;
    font-size: 28px;
}
#Explicación { text-align: center;
            width: 87%;
            height: 50px;
            display: inline-block;
            border: 2px solid #9933FF;
            color: #FF0033;
 }
#Actividad { text-align: left;
            width: 87%;
            height: 650px;
            display: block;
 }
 #columna {width: 12%;
    height: 503px;
    text-align: center;
    display: inline-block;
    float: right;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 120px;
    height: 100px;
    margin: 30px 100px;
    font-size: 25px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: white;
    background-color: orange;
    width: 120px;
    height: 100px;
    margin: 30px 130px;
    font-size: 35px;
    display: inline-block;
}
.caja{color: #FF9900;
        width: 100px;
        height: 100px;
        font-size: 50px;
        text-align: center;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 150px;
    font-size: 14px;  
    float: center;
}
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 60px;
        border: 3px solid #9933FF;
}
img {width: 60px;
    display: inline-block;
}
#pie {background: #99FFFF;
    text-align: center;
    width: 114%;
    height: 30px;
    border: 5px solid #9933FF;
    color: #FF0033;
    margin-top: 70px;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 105px;
        height: 105px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 60px;
    }
.raya {
        width: 105px;
        height: 10px;
        background-color:#000000;
    }
.sig {color: #000000;
        width: 30px;
        height: 105px;
        text-align: center;
        background-color: #33FFFF;
        border: 2px solid #33FFFF; 
        font-size: 60px;
}.tran {background-color: #33FFFF;
        width: 300px;
        height: 105px;
        border-top: 7px solid lightgreen;
        border-bottom: 7px solid lightgreen;
}#intentos{
    color: blue;
    font-size: 40px;
}#segundo{
    background-color: orange;
    margin: 0px 300px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 300px;
    display:  none;
}#mensajeok{
        font-size: 70px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 10px 200px;
        display: none;
}#mensajeno{
        font-size: 70px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 150px;
        display: none;
}#mensajefin{
        font-size: 70px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 150px;
        display: none;
}
<!--Para que no aparezcan las flechitas en la caja --> 
input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 
}
//Firefox:
input[type="number"] {
-moz-appearance: textfield;
}
input[type="number"]:hover,
input[type="number"]:focus {
-moz-appearance: number-input;
}
input[type=number] {
    -moz-appearance:textfield;
}
@media (min-width: 300px) { /*para teléfono pequeñísimo*/
   #cuerpo {
        height:900px;
}
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 95%;
        height: 25px;
        border: 3px solid #9933FF;
}
img {width: 17px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 50px;
    font-size: 20px;
}
#intentos{
    color: blue;
    font-size: 12px;
}#segundo{
    background-color: orange;
    margin: 0px 50px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 50px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 26px;
        height: 26px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 12px;
    }
    .caja{color: #FF9900;
        width: 20px;
        height: 20px;
        font-size: 11px;
        text-align: center;
}
#mensajeok{
        font-size: 20px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 5px 15px;
        display: none;
}#mensajeno{
        font-size: 20px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 15px;
        display: none;
}#mensajefin{
        font-size: 20px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 15px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 60px;
    height: 30px;
    margin: 5px 10px;
    font-size: 10px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 60px;
    height: 30px;
    margin: 5px 10px;
    font-size: 10px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 60px;
    height: 30px;
    margin: 5px 10px;
    font-size: 10px;  
    float: center;
}

}
    

@media (min-width: 430px) { /*para teléfono pequeño*/
    #cuerpo {
        height:900px;
}
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 95%;
        height: 35px;
        border: 3px solid #9933FF;
}
img {width: 25px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 150px;
    font-size: 22px;
}
#intentos{
    color: blue;
    font-size: 15px;
}#segundo{
    background-color: orange;
    margin: 0px 75px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 75px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 35px;
        height: 35px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 17px;
    }
    .caja{color: #FF9900;
        width: 25px;
        height: 25px;
        font-size: 15px;
        text-align: center;
}
#mensajeok{
        font-size: 25px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 5px 25px;
        display: none;
}#mensajeno{
        font-size: 25px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 25px;
        display: none;
}#mensajefin{
        font-size: 25px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 25px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 70px;
    height: 35px;
    margin: 5px 20px;
    font-size: 10px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 70px;
    height: 35px;
    margin: 5px 20px;
    font-size: 10px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 70px;
    height: 35px;
    margin: 5px 10px;
    font-size: 10px;  
    float: center;
}


   }


@media (min-width: 530px) { /* para teléfono */
    #cuerpo {
        height:900px;
}

#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 45px;
        border: 3px solid #9933FF;
}
img {width: 37px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 150px;
    font-size: 22px;
}
#intentos{
    color: blue;
    font-size: 23px;
}#segundo{
    background-color: orange;
    margin: 0px 125px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 125px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 45px;
        height: 45px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 28px;
    }
    .caja{color: #FF9900;
        width: 40px;
        height: 40px;
        font-size: 22px;
        text-align: center;
}
#mensajeok{
        font-size: 40px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 5px 75px;
        display: none;
}#mensajeno{
        font-size: 40px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 50px;
        display: none;
}#mensajefin{
        font-size: 40px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 5px 50px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 80px;
    height: 40px;
    margin: 15px 30px;
    font-size: 12px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 80px;
    height: 40px;
    margin: 15px 30px;
    font-size: 15px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 80px;
    height: 40px;
    margin: 15px 10px;
    font-size: 12px;  
    float: center;
}

    
}



@media (min-width: 650px) { /* para teléfono grande */
    #cuerpo {
        height:1200px;
}
    
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 50px;
        border: 3px solid #9933FF;
}
img {width: 45px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 175px;
    font-size: 25px;
}
#intentos{
    color: blue;
    font-size: 27px;
}#segundo{
    background-color: orange;
    margin: 0px 175px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 175px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 70px;
        height: 70px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 35px;
    }
    .caja{color: #FF9900;
        width: 60px;
        height: 60px;
        font-size: 35px;
        text-align: center;
}
#mensajeok{
        font-size: 50px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 10px 100px;
        display: none;
}#mensajeno{
        font-size: 50px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 75px;
        display: none;
}#mensajefin{
        font-size: 50px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 75px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 80px;
    height: 40px;
    margin: 30px 30px;
    font-size: 12px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 80px;
    height: 40px;
    margin: 30px 30px;
    font-size: 15px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 80px;
    height: 40px;
    margin: 30px 10px;
    font-size: 12px;  
    float: center;
}


}

@media (min-width: 768px) { /* para tablet */
    #cuerpo {
        height:1200px;
}
    #cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 52px;
        border: 3px solid #9933FF;
}
img {width: 50px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 200px;
    font-size: 26px;
}
#intentos{
    color: blue;
    font-size: 30px;
}#segundo{
    background-color: orange;
    margin: 0px 200px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 200px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 75px;
        height: 75px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 40px;
    }
    .caja{color: #FF9900;
        width: 65px;
        height: 65px;
        font-size: 38px;
        text-align: center;
}
#mensajeok{
        font-size: 52px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 10px 125px;
        display: none;
}#mensajeno{
        font-size: 52px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 100px;
        display: none;
}#mensajefin{
        font-size: 52px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 100px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 40px;
    font-size: 14px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 100px;
    height: 50px;
    margin: 30px 40px;
    font-size: 17px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 10px;
    font-size: 14px;  
    float: center;
}

}
@media (min-width: 900px) { /* para tablet grande */
    #cuerpo {
        height:1200px;
}
    
    #cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 55px;
        border: 3px solid #9933FF;
}
img {width: 55px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 250px;
    font-size: 28px;
}
#intentos{
    color: blue;
    font-size: 35px;
}#segundo{
    background-color: orange;
    margin: 0px 250px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 250px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 80px;
        height: 80px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 45px;
    }
    .caja{color: #FF9900;
        width: 75px;
        height: 75px;
        font-size: 45px;
        text-align: center;
}
#mensajeok{
        font-size: 55px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 10px 150px;
        display: none;
}#mensajeno{
        font-size: 55px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 125px;
        display: none;
}#mensajefin{
        font-size: 55px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 125px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 80px;
    font-size: 14px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 100px;
    height: 50px;
    margin: 30px 80px;
    font-size: 17px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 10px;
    font-size: 14px;  
    float: center;
}

}
@media (min-width: 1140px) { /* para ordenador */
    #cuerpo {
        height:900px;
}
    
#cabecera {background: #FFCCFF;
        padding: 10px;
        width: 97%;
        height: 60px;
        border: 3px solid #9933FF;
}
img {width: 60px;
    display: inline-block;
}
article {color: #000000;
    display: inline-block;
    margin: 0px 300px;
    font-size: 28px;
}
#intentos{
    color: blue;
    font-size: 40px;
}#segundo{
    background-color: orange;
    margin: 0px 300px;
    display: none;
}#ultimo{
    background-color: orange;
    margin: 0px 300px;
    display:  none;
}
#tabla2,#tabla3 {
        margin: 10px auto;
        background-color: #FFFFFF;
}
.celda {color: #000000;
        width: 105px;
        height: 105px;
        text-align: center;
        border: 2px solid #FF9900; 
        font-size: 60px;
    }
    .caja{color: #FF9900;
        width: 100px;
        height: 100px;
        font-size: 50px;
        text-align: center;
}
#mensajeok{
        font-size: 70px;
        color: #9933FF;
        background-color: white;
        text-align: center;
        margin: 10px 200px;
        display: none;
}#mensajeno{
        font-size: 70px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 150px;
        display: none;
}#mensajefin{
        font-size: 70px;
        color: #9933FF;
        background-color:white;
        text-align: center;
        margin: 10px 150px;
        display: none;
}
#Siguiente { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 100px;
    font-size: 14px;
}#Volver { 
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color:#FFCCFF;
    width: 100px;
    height: 50px;
    margin: 30px 100px;
    font-size: 17px;
    display: inline-block;
}
#Comprobar {
    border-radius: 10px;
    padding-bottom: initial;
    color: #FFFFFF;
    background-color: #9933FF;
    width: 100px;
    height: 50px;
    margin: 30px 100px;
    font-size: 14px;  
    float: center;
}
}