html,
body,
.bg {
  width: 100%;
  height: 100%;
}
.bg {
  background-image: url('https://unsplash.it/1800/1600?image=703');
  background-repeat: no-repeat;
  background-size: cover;
  background-position: center center;
  transition: all ease-out 0.3s;
}
.container {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}
.input-group {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  display: table;
  width: 300px;
  height: 30px;
  box-sizing: border-box;
}
.input-group .txt,
.input-group .btn {
  display: table-cell;
  width: 60%;
  box-sizing: border-box;
  border: 0;
  padding: 5px 10px;
  height: 30px;
}
.input-group .btn {
  outline: 0;
  width: 40%;
  background-color: rgba(0, 0, 0, 0.8);
  color: #ffffff;
}