style.css

* {
    box-sizing: border-box;
}

html, body{
    height: 100%;
    width: 100%;
    margin: 0;
    padding: 0;
}

.screen{
    display: flex;
    flex-flow: column;
    height: 100%;
}

.control-bar{
    padding: 0.3rem;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
    align-items: center;
}

#container {
    flex-grow: 1;
    display: flex;
    justify-content: center;
    align-items: center;
}

#grid {
    -webkit-touch-callout: none; /* iOS Safari */
    -webkit-user-select: none; /* Safari */
    -khtml-user-select: none; /* Konqueror HTML */
    -moz-user-select: none; /* Old versions of Firefox */
    -ms-user-select: none; /* Internet Explorer/Edge */
    user-select: none; /* Non-prefixed version, currently*/

    border-collapse: collapse;
    border: 2px solid rgb(12, 53, 71);
}
  
#grid td{
    border: 1px solid rgb(175, 216, 248);
    text-align: center;
}

#grid td img{
    display: block;
    margin-left: auto;
    margin-right: auto;
}

.button {
    background-color: rgb(12, 53, 71); 
    border: none;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    text-align: center;
    text-decoration: none;
    font-size: 14px;
    cursor: pointer;
    border-radius: 4px;
    padding: 0.3rem;
    margin: 0.1rem;
    width: 8rem;
}

select {
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    outline: none;
    border: none;
    cursor: pointer;
    width: 10rem;
    padding: 0.2rem;
    color: rgb(12, 53, 71);
    font-family: Arial, Helvetica, sans-serif;
}

.control-select {
    border: 1px solid rgb(12, 53, 71);
    position: relative;
    overflow: hidden;
}

.control-select::after {
    content: "\25BC";
    font-size: 12px;
    position: absolute;
    background: rgb(12, 53, 71);
    color: white;
    top: 0;
    right: 0;
    padding: 0.2rem;
    pointer-events: none;
    transition: all 0.3s ease;
}

.control-select:hover::after {
    background: white;
    color: rgb(12, 53, 71);
}

.pop-up-background {
    position: fixed;
    left: 0;
    top: 0;        
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    /* opacity: 0; */
    /* visibility: hidden; */
    transform: scale(1.1);
    transition: visibility 0s linear 0.25s, opacity 0.25s 0s, transform 0.25s;
}

.pop-up {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: white;
    padding: 1rem 1rem;
    width: 24rem;
    color: rgb(12, 53, 71);
    border: 3px solid rgb(12, 53, 71);
    border-radius: 0.5rem;
    font-family: Arial, Helvetica, sans-serif;
}

.pop-up h2 {
    margin-bottom: auto;
}

.pop-up-close-button {
    float: right;
    width: 4rem;
    line-height: 2rem;
    text-align: center;
    font-family: Arial, Helvetica, sans-serif;
    font-size: medium;
    color: white;
    cursor: pointer;
    background-color: rgb(12, 53, 71);
    border-radius: 0.25rem;
}

/*Classes*/
.unvisited{
    animation: none;
    background: none;
    border: 1px solid rgb(175, 216, 248);
}

.wall{
    animation-name: wall-fill;
    animation-duration: 0.3s;
    animation-timing-function: ease-out;
    animation-fill-mode: forwards;
}

.visited{
    animation-name: visited-fill;
    animation-duration: 1.5s;
    animation-timing-function: ease-out;
    animation-fill-mode: forwards;
}

.real-time-visited{
    background-color: rgba(0, 190, 218, 0.75);
}

.path{
    animation-name: path-fill;
    animation-duration: 0.5s;
    animation-timing-function: ease-out;
    animation-fill-mode: forwards;
}

.real-time-path{
    background-color: rgb(231, 220, 57);
    border: 1px solid rgb(231, 220, 57) !important;
}

/*Animations*/
@keyframes wall-fill{
    0%{
        transform: scale(.3);
        background-color: rgb(12, 53, 71);
    }
    
    50%{
        transform: scale(1.2);
        background-color: rgb(12, 53, 71);
    }
    
    100%{
        transform: scale(1.0);
        background-color: rgb(12, 53, 71);
        border: 1px solid rgb(12, 53, 71);
    }
}

@keyframes visited-fill{
    0% {
        transform: scale(.3);
        background-color: rgba(0, 0, 66, 0.75);
        border-radius: 100%;
    }
    
    50% {
        background-color: rgba(17, 104, 217, 0.75);
    }
    
    75% {
        transform: scale(1.2);
        background-color: rgba(0, 217, 159, 0.75)
    }
    
    100% {
        transform: scale(1.0);
        background-color: rgba(0, 190, 218, 0.75);
    }
}

@keyframes path-fill{
    0%{
        transform: scale(.3);
        background-color: rgb(231, 220, 57);
    }
    
    50%{
        transform: scale(1.2);
        background-color: rgb(231, 220, 57);
    }
    
    100%{
        transform: scale(1.0);
        background-color: rgb(231, 220, 57);
        border: 1px solid rgb(231, 220, 57);
    }
}