<section>
  <button class="button1">フワッ</button>
  <button class="button2">シュインッ</button>
  <button class="button3">ブオン</button>
  <button class="button4">ファッ</button>
  <div class="button5-wrapper">
    <button class="button5">ジュワッ</button>
  </div>
</section>

* {
  font-family: "Hiragino Kaku Gothic ProN", "ヒラギノ角ゴ ProN W3", Meiryo;
  text-decoration: none;
  outline: none;
}

$font1: #fff;
$color1: #3a3a4d;
$color2: #7f7f8f;
$color3: #e35583;
$base: #484860;

[class^="button"] {
  &:hover {
    cursor: pointer;
  }
}

.button1 {
  font-size: 21px;
  color: $font1;
  line-height: 1;
  padding: 15px 30px;
  background-color: $color1;
  border: 1px solid $color1;
  transition: all .2s linear;
  &:hover {
    border-color: $font1;
    background-color: transparent;
  }
}

.button2 {
  font-size: 21px;
  color: $font1;
  line-height: 1;
  padding: 15px 30px;
  background-color: transparent;
  border: none;
  position: relative;
  transition: all .2s linear;
  &:before, &:after {
    content: "";
    display: block;
    width: 0;
    height: 0;
    position: absolute;
    border-color: transparent;
    transition: all .2s linear;
    z-index: 2;
    box-sizing: border-box;
  }
  &:before {
    top: 0;
    left: 0;
    border-top: 1px solid transparent;
    border-left: 1px solid transparent;
  }
  &:after {
    bottom: 0;
    right: 0;
    border-bottom: 1px solid transparent;
    border-right: 1px solid transparent;
  }
  &:hover {
    color: $color2;
    &:before, &:after {
      border-color: $color2;
      width: 100%;
      height: 100%;
      transition: width .2s linear, height .2s linear;
    }
  }
}

.button3 {
  font-size: 21px;
  color: $font1;
  line-height: 1;
  padding: 15px 30px;
  background-color: transparent;
  border: none;
  transition: all .3s linear;
  &:hover {
    text-shadow: 
      0px 0px 30px $color3,
      0px 0px 18px $color3,
      0px 0px 18px $color3;
  }
}

.button4 {
  font-size: 21px;
  color: $font1;
  line-height: 1;
  padding: 15px 30px;
  background-color: $color1;
  border: none;
  outline: 2px solid;
  outline-color: rgba($color1, 1.0);
  outline-offset: 0px;
  transition: none;
  &:hover {
    transition: all .4s ease-out;
    box-shadow: 0 0 20px rgba($color1, .7);
    outline-color: rgba($color2, 0);
    outline-offset: 15px;
  }
}

.button5-wrapper {
  margin-top: 30px;
  width: 100%;
  .button5 {
    width: 100%;
    font-size: 21px;
    color: $font1;
    line-height: 1;
    padding: 15px 30px;
    background-color: transparent;
    border: 1px solid $font1;
    transition: all .2s linear;
    &:hover {
      background-color: rgba($color2, .3);
    }
  }
}

html,body {
  margin: 0;
  width: 100vw;
  min-width: 580px;
  height: 100vh;
  position: relative;
  background-color: $base;
}
section {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  position: absolute;
  top: 50%;
  left: 50%;
  width: 600px;
  transform: translate(-50%, -50%);
}