/* the reset selector */
* {
    margin: 0;
    padding: 0;
}

/* the styles for the body */
body {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 100%;
}

#bg_pic {
	position: fixed; 
	width: 100%; 
	height: 100%;
	overflow:hidden
}

#bg_pic img  {
	width: 100%;
    height: 100%; 
	object-fit:cover;
}

#loading {
	opacity: 1;
	animation: fade 2s ease-in-out;
	animation-iteration-count: 1;
}
@keyframes fade {
  0% {opacity: 0;}
  100% {opacity: 1;}
}

#en_pic img, #sp_pic img, #cn_pic img {
    width: 100%;
    transition: 2s;
}

#en_pic img:hover, #sp_pic img:hover, #cn_pic img:hover {
    transform: scale(1.2);
    filter: drop-shadow(8px 8px 10px yellow);
}


/* the styles for the English picture */
#en_pic {
    width: 17%;
    filter: drop-shadow(8px 8px 10px gray);
    position: fixed;
    left: 20%;
    top: 10%;
    animation: landing_en 5s ease-in-out 0s 1;
}

@keyframes landing_en {
    from {
        top: 26%;
        left: 5%;
        transform: scale(0.1);
    }

    to {
        top: 10%;
        left: 20%;
        transform: scale(1);
    }
}


/* the styles for the Spanish picture */
#sp_pic {
    width: 15%;
    filter: drop-shadow(8px 8px 10px gray);
    position: fixed;
    right: 20%;
    top: 15%;
    animation: landing_sp 5s ease-in-out 0s 1;
}

@keyframes landing_sp {
    from {
        top: 30%;
        right: 3%;
        transform: scale(0.1);
    }

    to {
        top: 15%;
        right: 20%;
        transform: scale(1);
    }
}


/* the styles for the Chinese picture */
#cn_pic {
    width: 36%;
    position: fixed;
    left: 32%;
    top: 25%;
    filter: drop-shadow(8px 8px 10px gray);
    animation: landing_cn 5s ease-in-out 0s 1;
}

@keyframes landing_cn {
    from {
        top: 40%;
        left: 10%;
        transform: scale(0.2);
    }

    to {
        top: 25%;
        transform: scale(1);
    }
}



/* the styles for the nav */
nav {
    position: fixed;
    left: 10%;
    right: 10%;
    bottom: 15%;

}

ul {
    display: flex;
    justify-content: center;
    flex-direction: row;
    list-style-type: none;
    width: 100%
}

li {
    width: 30%;
    margin: 0 10px;
    text-align: center;
}

a {
    text-decoration: none;
    color: white;
}

/* the styles for the button */
.btn-flip {
    opacity: 1;
    outline: 0;
    width: 100%;
    line-height: 40px;
    position: relative;
    text-align: center;
    display: inline-block;
    border-radius: 15px;

}

.btn-flip:hover:after {
    opacity: 1;
    -webkit-transform: translateY(0) rotateX(0);
    transform: translateY(0) rotateX(0);
}

.btn-flip:hover:before {
    opacity: 0;
    -webkit-transform: translateY(50%) rotateX(90deg);
    transform: translateY(50%) rotateX(90deg);
}

.btn-flip:after {
    top: 0;
    left: 0;
    opacity: 0;
    width: 100%;
    color: white;
    display: block;
    -webkit-transition: 0.5s;
    transition: 0.5s;
    position: absolute;
    background: #f1b24a;
    content: attr(data-back);
    -webkit-transform: translateY(-50%) rotateX(90deg);
    transform: translateY(-50%) rotateX(90deg);
}

.btn-flip:before {
    top: 0;
    left: 0;
    opacity: 1;
    color: white;
    display: block;
    padding: 0 30px;
    line-height: 40px;
    -webkit-transition: 0.5s;
    transition: 0.5s;
    position: relative;
    background: #9dc88d;
    content: attr(data-front);
    -webkit-transform: translateY(0) rotateX(0);
    transform: translateY(0) rotateX(0);
}



/* tablet portrait */
@media only screen and (max-width: 959px) {
    body {
        font-size: 72%;
    }
}

/* mobile landscape */
@media only screen and (max-width: 767px) {
    body {
        font-size: 50%;
    }
}

/* mobile portrait */
@media only screen and (max-width: 479px) {
    ul {
        flex-direction: column;
    }

    li {
        width: 60%;
        margin: 10px auto;
    }

    #en_pic {
        width: 25%;
        left: 20%;
        top: 10%;
    }

    @keyframes landing_en {
        from {
            top: 12%;
            left: -10%;
            transform: scale(0.1);
        }

        to {
            top: 10%;
            left: 20%;
            transform: scale(1);
        }
    }

    #sp_pic {
        width: 25%;
        right: 20%;
        top: 15%;
    }

    @keyframes landing_sp {
        from {
            top: 18%;
            right: -10%;
            transform: scale(0.1);
        }

        to {
            top: 15%;
            right: 20%;
            transform: scale(1);
        }
    }

    #cn_pic {
        width: 66%;
        left: 17%;
        top: 25%;
    }

    @keyframes landing_cn {
        from {
            top: 30%;
            left: -10%;
            transform: scale(0.2);
        }

        to {
            top: 25%;
            transform: scale(1);
        }
    }


}