assets/css/style.css
/* Main css stylesheet */

@import 'https://fonts.googleapis.com/css?family=Lato:900,300';

html, body {
  /* Margin & Padding */
  margin: 0; padding: 0;

  /* Global text params */
  font-family: Lato, sans-serif;
  font-size: 16px;

  /* Background */
  background-size: cover;
  background-image: url(../imgs/background.jpg);
  background-repeat: no-repeat;
  background-position: center;
  background-attachment: fixed;

  /* Size */
  height: 100%; width: 100%;
}

/* Text */
h1 {
  margin: 0;
}
h6 {
  margin: 0;
  opacity: .7;
}

/* Textareas */
textarea {
  width: 100%; height: 50vh;
  border: none; border-radius: 4px;
  padding: 8px;

  word-wrap: break-word;
  word-break: break-all;
  box-sizing: border-box;
  resize: none;
}

/* Buttons */
button {
  /* Style */
  color: black;
  cursor: pointer;
  background-color: white;
  border: 1px solid white;

  /* Size */
  width: 128px;
  height: 32px;

  /* Animation */
  transition: .2s;
}
button:not(:disabled):hover {
  /* Style */
  background-color: transparent;
  color: white;

  /* Animation */
  transition: .2s;
}
button:disabled {
  /* Style */
  color: white;
  background-color: transparent;

  /* Back pattern */
  background-size: 32px 32px;
  background-image: linear-gradient(135deg, rgba(255, 255, 255, 1) 25%, transparent 25%,
                      transparent 50%, rgba(255, 255, 255, 1) 50%, rgba(255, 255, 255, 1) 75%,
                      transparent 75%, transparent);

  cursor: default;

  /* Opacity */
  opacity: .5;
}

/* Top bar */
.menu {
  position: absolute;
  top: 0;

  width: 100%;
}
.menu a {
  float: right;
  margin: 16px;

  text-transform: uppercase;
  text-decoration: none;
  color: white;

  transition: .2s;
}
.menu a:hover {
  transition: .2s;
  color: black;
}

/* Page organization */
.group {
  /* Size */
  width: 100%; height: 100%;

  /* Center parts */
  display: flex;
  flex-wrap: wrap;
}

.part {
  /* Position */
  margin: 0 1.5%; padding: 16px;
  align-self: center;
  width: 30%;
  float: left;

  box-sizing: border-box;
  border-radius: 4px;

  /* Separation */
  /*box-shadow: 0 0 20px 0 rgba(0, 0, 0, 0.2), 0 5px 5px 0 rgba(0, 0, 0, 0.24);*/

  /* Text */
  color: white;
}

@media (max-width: 860px) {
  .part {
    width: 100%;
  }

  .input {
    margin-top: 28px;
  }
}

/* Elements */
.process {
  /* Center text */
  text-align: center;
}

/* Info/error tooltip */
.tooltip {
  position: relative;
  width: 100%;

  display: none;
  z-index: 2;
}
.tooltip > span {
  /* Size */
  position: absolute;
  width: 90%;

  /* Position */
  left: 50%;
  transform: translateX(-50%);
  margin-top: 12px;
  z-index: -1;

  /* Style */
  text-align: left;
  border-radius: 4px;
  white-space: pre-wrap;
  padding: 4px;
  color: white;
}
.tooltip > span::before {
  content: "";
  position: absolute;
  bottom: 100%;
  left: 50%;
  margin-left: -8px;
  border-width: 8px;
  border-style: solid;
}
.tooltip.info > span {background-color: #029bc9;}
.tooltip.info > span::before {border-color: transparent transparent #029bc9 transparent;}

.tooltip.error > span {background-color: #cc0000;}
.tooltip.error > span::before {border-color: transparent transparent #cc0000 transparent;}

.combined-but > button {
  width: 112px;
  border-right: 0;
}
.combined-but > select {
  /* Postion */
  position: absolute;

  /* Style */
  color: transparent;
  border: 1px solid white;

  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;

  background: url(../imgs/arrow-down.png) no-repeat white center;

  /* Size */
  width: 16px;
  height: 32px;
}
.combined-but > select option {
  /* Style */
  color: black;
}
.combined-but > select:disabled {
  /* Postion */
  opacity: .5;
}
