here is what i added:

.vote {
    padding: .5rem 1.5rem;
    text-align: center
}

.vote * {
    display: block
}

.vote-score {
    font-weight: 700
}

.vote-button {
    border: none;
    background: #789;
    padding: 16px;
    color: white;
    line-height: 1.15;
    white-space: nowrap;
    border-radius: 12px;
}

/* remove this if u want to be symmetrical */
.vote-down {
    padding: 6px 16px 6px 16px;
    white-space: nowrap;
    border-radius: 8px;
    line-height: 0.5;
    display: flex;
    justify-content: center
}

.vote-user-upvoted .vote-up {
    color: white;
    background: orange;
}

.vote-user-downvoted .vote-down {
    background: #0080ff;
    color: white;
}

.submission-nav a {
  display: inline-block;
  padding: 8px;
  margin: 4px;
}