* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    background-color: #fefefe;
    padding: 50px 0;
}
.col-md-1, .col-md-4, .col-md-7, .col-md-6 {
    float: left;
}
.clr {
    clear: both;
}
.brace {
    height: 230px;
}
.title {
    color: rgb(25, 41, 16);
}
.text-primary {
    margin: 15px 0;
}
.text-3 {
    margin-bottom: 40px;
}
#result-show {
    font-size: 28px;
    line-height: 42px;
}
.equation label, .col-md-6 p {
    font-size: 35px;
    color: rgb(99, 97, 255);
    font-weight: bold;
}
.equation label input {
    width: 85px;
    height: 50px;
    font-size: 23px;
    font-weight: bold;
    outline: none;
    border: 1px solid blue;
    color: blue;
    padding: 3px 13px;
    border-radius: 6px;
    transition: .3s ease;
}
.equation label input:focus {
    box-shadow: 0 0 5px rgb(0, 136, 255);
}
.realLifeImg, .geometricImg {
    width: 70%;
    height: 300px;
    display: block;
    border-radius: 10px;
    box-shadow: 0 0 5px black;
    margin: 20px auto;
}
.empty-set, .one-solution, .infinite-solutions {
    animation: show 1.5s ease;
    display: none;
}
@keyframes show {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

/* Responsive */
@media only screen and (max-width: 1199px) {
    .title {
        font-size: 35px;
    }
    .text-primary {
        font-size: 26px;
    }
    .text-3 {
        font-size: 18px;
    }
    .equation label input {
        width: 60px;
    }
    .equation label, .col-md-6 p {
        font-size: 30px;
    }
    .btn {
        font-size: 18px!important;
    }
    #result-show {
        font-size: 24px;
        line-height: 39px;
    }
    .realLifeImg, .geometricImg {
        width: 85%;
    }
}

@media only screen and ( max-width: 991px ) {
    body {
        padding: 30px 0;
    }
    .title {
        font-size: 26px;
    }
    .text-primary {
        font-size: 19.7px;
        margin: 13px 0;
    }
    .col-md-1 {
        max-width: calc(100% / 12 * 2);
    } 
    .col-md-7 {
        max-width: calc(100% / 12 * 10);
        margin-bottom: 50px;
    }
    .col-md-4 {
        max-width: 100%;
    }
    #result-show {
        font-size: 30px;
        line-height: 40px;
    }
    .realLifeImg, .geometricImg {
        width: 100%;
        height: 290px;
    }
}

@media only screen and ( max-width: 767px ) { 
    .title {
        font-size: 30px;
        margin: 0 30px;
    }
    .text-primary {
        font-size: 20px;
        margin: 13px 30px;
    }
    .equation label input {
        width: 55px;
        height: 45px;
        padding: 0px 10px;
        font-size: 22px;
    }
    .equation label, .col-md-6 p {
        font-size: 25px;
    }
    .brace {
        height: 200px;
        width: 130px;
    }
    .realLifeImg, .geometricImg {
        width: 85%;
        height: 300px;
    }
}

@media only screen and ( max-width: 575px ) {
    .title {
        font-size: 21px;
        margin: 0 10px;
    }
    .text-primary {
        font-size: 18px;
        margin: 13px 25px;
    }
    .text-3 {
        font-size: 16px;
    }
    .col-md-1 {
        max-width: 0;
        display: none;
    } 
    .col-md-7 {
        max-width: 100%;
        margin-bottom: 30px;
    }
    .equation label input {
        width: 42px;
        height: 40px;
        padding: 0px 7px;
        font-size: 21px;
    }
    .equation label, .col-md-6 p {
        font-size: 20px;
    }
    #result-show {
        font-size: 24px;
        line-height: 37px;
    }
    .realLifeImg, .geometricImg {
        width: 100%;
        height: 290px;
    }
}