styles.css

* {
    box-sizing: border-box;
    margin: 0;
}

body {
    font-family: Roboto;
    background-color: #F1F5F8;
}

main {
    display: flex;
    flex-flow: column nowrap;
    align-items: center;
    gap: 15px;
    margin-top: 15vh;
}

h1, .saver-text {
    font-size: 6.45rem;
    font-weight: 600;
    letter-spacing: 6px;
    color: #102B42;
    user-select: none;
}

.saver-text {
    user-select: auto;
    font-weight: 625;
    letter-spacing: 2px;
    font-size: 3rem;
}

.saver-text::selection, #saved-values::selection {
    background-color: #102B42;
    color: #F1F5F8;
}

p {
    font-size: 12rem;
    font-family: 'Open Sans';
    font-weight: 550;
    color: rgb(0, 0, 200);
}

.buttons {
    display: flex;
    flex-flow: row nowrap;
    gap: 1.75vw;
}

.decrease, .reset, .increase, .save, .clear {
    font-family: Roboto;
    font-size: 1.25rem;
    font-weight: 400;
    letter-spacing: 5px;
    background: transparent;
    height: 2.3rem;
    border: 3.5px solid #000000;
    border-radius: 10px;
    box-shadow: 0 0 10px 0.1px #BBBBBB;
    cursor: pointer;
}

.reset {
    min-width: 6.25vw;
}

button:not(.reset) {
    min-width: 11vw;
}

.save {
    width: 32vw;
    background-color: rgb(0, 170, 0);
    border-color: rgb(0, 127, 0);
    color: #F1F5F8;
}

.clear {
    width: 32vw;
    background-color: rgb(200, 0, 0);
    border-color: rgb(157, 0, 0);
    color: #F1F5F8;
}

.decrease:hover, .reset:hover, .increase:hover {
    transition: background-color 0.5s ease-in-out;
    background-color: #D0D3D6;
}

.save:hover, .clear:hover {
    transition: background-color 0.5s ease-in-out, border-color 0.5s ease-in-out, color 0.5s ease-in-out;
    background-color: #D0D3D6;
    border-color: #F1F5F8;
    color: #102B42;
}

.decrease:active, .reset:active, .increase:active, .save:active, .clear:active {
    transition: box-shadow 0.1s ease-in-out;
    box-shadow: 0 0 0 2px #47A3E7;
}

.number::selection {
    color: #F1F5F8;
    background-color: rgb(0, 0, 200);
}

.green::selection {
    color: #F1F5F8;
    background-color: rgb(0, 160, 0);
}

.blue::selection {
    color: #F1F5F8;
    background-color: rgb(0, 0, 200);
}

.red::selection {
    color: #F1F5F8;
    background-color: rgb(200, 0, 0);
}