body {
  background-image: url(bg.jpg);
  background-repeat: no-repeat;
  background-size: cover;
}
.intro {
  text-align: center;
}
.intro .h1 {
  margin: 0 auto;
  text-align: center;
}
.panel-group {
  overflow: hidden;
  display: block;
  margin: auto ;
  margin-left: 34%;
}
.btn-group {
  width: 100%;
  top: 0;
  left: 0;
  margin: 0;
}
.btn-group button {
  text-align: left;
}
.panel-collapse div {
  width: 100%;
  height: 100%;
  padding: 0;
  margin: 0;
}
.panel-collapse div div {
  padding: 0;
  margin: 0;
  width: 100%;
  height: 100%;
}