styles.css

* {
    margin: 0; padding: 0;
    background-color: var(--black);
    text-align: center;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    color: var(--white);
}
.green {
    border-color: var(--green);
    color: var(--green);
}
.red {
    border-color: var(--red_alt);
    color: var(--red_alt);
}

body { min-width: 350px; }

header {
    height: 40px;
    min-width: 260px;
    margin: 10px 0;
    border-bottom: solid 1px var(--black_alt);
    padding-bottom: 10px;
}

main {
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: calc(92vh - 42px);
}

footer {
    display: flex;
    justify-content: space-around;
    border-top: solid 1px var(--black_alt);
    padding: 10px;
}

.field {
    margin: 15px 0;
    border: solid 2px var(--black_alt);
    border-radius: 10px;
    padding: 15px 25px 10px;
}
.field > div, .secret-key { position: relative; }

h2 {
    margin: -30px 0 10px;
    background-color: var(--black);
    color: var(--white_alt);
}

label {
    display: block;
    margin: 5px 0;
}

input, select {
    width: 200px;
    height: 20px;
    margin-bottom: 5px;
    border: solid 1px var(--black_alt);
    border-radius: 5px;
    text-align: left;
    color: var(--white_alt);
    padding: 1px 5px;
}
i { color: var(--blue_alt); }

input::-webkit-outer-spin-button, input::-webkit-inner-spin-button, input[type=number] {
  -webkit-appearance: none;
  -moz-appearance: textfield;
}

select {
    width: 212px;
    height: 24px;
}

button {
    cursor: pointer;
    width: 24px;
    height: 24px;
    border-radius: 5px;
    border: solid 1px;
}

.input-buttons {
    position: absolute;
    right: 15px;
    bottom: 5px;
    background: none;
}

.input-button {
    background: none;
    border: none;
}

.remove-button {
    position: absolute;
    margin-left: 5px;
}
.remove-button:hover {
    background-color: var(--red_alt);
    color: var(--black);
}

#add-secret-key {
    margin-top: 5px;
    border-color: var(--green_alt);
    color: var(--green_alt);
}
#add-secret-key:hover {
    background-color: var(--green_alt);
    color: var(--black);
}

#only-letters-and-numbers {
    width: 15px;
    margin-left: 5px;
    translate: 0 4px;
}

#make-password-button {
    width: 100%;
    height: 30px;
    margin-bottom: 5px;
    border: solid 2px;
    font-size: 15px;
    font-weight: bold;
}
#make-password-button:hover {
    background-color: var(--green);
    color: var(--black);
}