.container {
  flex: 1;
  flex-direction: column;
  justify-content: center;
}

.maincard {
  width: 20em;
  min-height: 41em;
  align-items: center;
  /*justify-content: center;*/
  margin: 4em;
  /*vertical-align: baseline;*/
}

.halfwidth {
  width: 50%;
  flex: 1;
  text-align: left;
}

.fullwidth {
  width: 100%;
  display: flex;
}

.right {
  margin-left: auto;
}

.flex {
  display: flex;
}

@media screen and (min-height: 45em) {
  .container {
    display: flex;
  }
}

.container {
  flex: 1;
  flex-direction: column;
  justify-content: center;
}

.maincard {
  width: 20em;
  min-height: 41em;
  align-items: center;
  /*justify-content: center;*/
  margin: 4em 0;
  /*vertical-align: baseline;*/
}

.halfwidth {
  width: 50%;
  flex: 1;
  text-align: left;
}

.fullwidth {
  width: 100%;
  display: flex;
}

.right {
  margin-left: auto;
}

.flex {
  display: flex;
}

@media screen and (min-height: 45em) {
  .container {
    display: flex;
  }
}

Remove left & right margin
Remove left & right margin
