html, body {
    margin: 0;
    padding: 0;
    font-family: 'Arial', sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    /*select none*/
    user-select: none;
}

header, footer{
    margin:0;
    width: 100%;
    background: black;
    color: white;
    padding-top:0.6em;
    padding-bottom:0.6em;
    text-align: center;
}

header h1 a{
    color: white;
    text-decoration: none;
}

footer{
    padding-top:1.5em;
    padding-bottom:1.5em;
    right: 0; bottom: 0; left: 0;
}


.ct_btns{
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    position: sticky;
    top: 0em;
    background: white;
    width: 100%;
    z-index: 6;
}

.ct_btn{
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    width: 8em;
    text-align: center;
    padding: 0.5em;
    background: black;
    color: white;
    margin:0.5em;
    border-radius:3em;
    cursor: pointer;

}


.ct_btn:hover{
    transition: 0.3s;
    animation: btn_pulse 1s infinite;
    background: #333333;
    color:white;
}

#new_sdg_btn{
    animation: btn_pulse 1s infinite;
}

@keyframes btn_pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(0, 0, 0, 0.7);
    }
    70% {
        box-shadow: 0 0 0 5px rgba(0, 0, 0, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(0, 0, 0, 0);
    }
}


.pre_operate{
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
}
.m_material{
    display: flex;
    flex-direction: column;
    justify-content: start;
    align-items: center;
    text-align: center;
    margin:0.5em;
    width: 18em;
    height:9em;
    color: black;
}

.sdg_box{
    width: 90%;
    height: 100%;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
}

#new_sdg_box{
    margin-bottom: 1em;
}

.sdg_img{
    width: 16%;
    height: 100%;
    object-fit: cover;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    margin: 2%;
    /*padding: 1%;*/
    transition: 0.3s;
    cursor: pointer;
}

.sdg_img img{
    width: 100%;
    height: 100%;
    /*object-fit: cover;*/
    border-radius: 10px;
}

.sdg_img:hover{
    /*transform: scale(1.1) rotate(3deg);*/
    animation: pulse 1s infinite;
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
    filter: brightness(1.1);
}

#sdg_img_18{
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(0, 0, 0, 0.7);
    }
    70% {
        transform: scale(1.1);
        box-shadow: 0 0 0 10px rgba(0, 0, 0, 0);
    }
    100% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(0, 0, 0, 0);
    }
}

#sdg_img_18{
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
}

/*insert word in certain sdg pic*/
#sdg_img_18::after{
    content: "NEW GOALs";
    position: absolute;
    top: 50%;
    left: 50%;
    display: none;
    transform: translate(-50%, -50%);
    color: white;
    width: 100%;
    height: 100%;
    text-align: center;
    font-size: 1.2em;
    font-weight: bold;
    text-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
    background: rgba(0, 0, 0, 0.5);
    border-radius: 10px;
}

#sdg_img_18:hover::after{
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

/*quick guide*/
.quick_guide{
    display: flex;
    text-align: center;
    flex-direction: column;
    justify-items: center;
    align-items: center;
    margin-top: 1em;
}

.quick_guide a {
    color: black;
}

.arrow_hint_bx{
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    margin-top: 1em;
    margin-bottom: 1em;
}

.arrow_hint{
    content:'';
    width: 0;
    height: 0;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
    border-top: 10px solid black;
    animation: arrow_hint 1s infinite;
    /*show & disappear*/
}

@keyframes arrow_hint {
    0% {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
    100% {
        opacity: 0;
    }
}

/*help_btn*/
.help_btn{
    display: flex;
    justify-content: center;
    align-items: center;
    position: fixed;
    bottom: 0.5em;
    right: 0.5em;
    width: 4.5em;
    height: 4.5em;
    color: white;
    cursor: pointer;
}

.help_btn img{
    width: 3.5em;
    height: auto;
    border-radius: 50%;
    transition: 0.3s;
    box-shadow: 0px 0px 20px rgba(255, 0, 255, 0.5);
}

.help_btn_txt::after{
    content: "About";
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    display: none;
    color: white;
    font-size: 0.8em;
    font-weight: bold;
    text-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
}

.help_btn:hover .help_btn_txt::after{
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.help_btn:hover img{
    filter: brightness(1.5);
    box-shadow: -1px 0px 2px rgba(255, 0, 255, 0.5), 
              0px -1px 4px rgba(255, 0, 255, 0.5), 
              1px 0px 6px rgba(255, 0, 255, 0.5), 
              0px 1px 12px rgba(255, 0, 255, 0.5);
}

::-webkit-scrollbar{
    width: 0.7rem;
}
  
::-webkit-scrollbar-track{
    background-color: transparent;
}
  
::-webkit-scrollbar-thumb{
    background-color: #d6dee1;
    border-radius: 0.7rem;
    border: 0.1rem solid transparent;
    background-clip: content-box;
}

::-webkit-scrollbar-thumb:hover{
    background-color: #a8bbbf;
}

/*RWD*/
@media screen and (max-width: 1024px){
    .sdg_img{
        width: 30%;
        height: 100%;
        margin: 1%;
    }

    .pre_operate{
        flex-direction: column;
    }
}