* {
  margin: 0;
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
    sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.App {
  margin-left: auto;
  margin-right: auto;
  margin-top: 1em;
  text-align: center;
  width: 50%;
  min-height: 90vh;
  display: flex;
  flex-direction: column;
}

.app-header {
  padding: 1em;
}

.top-header {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

.form {
  padding: 1em;
}

.form * {
  padding: 0.5em 1em 0.5em 1em;
}

.form label {
  font-weight: 600;
}

.form-input {
  text-align: center;
}

.form-input:not(:placeholder-shown):invalid {
  border: 2px solid red;
}

.form-button {
  margin-left: 1em;
  color: white;
  background-color: rgba(0, 0, 0, 0.7);
  border: 2px solid rgba(0, 0, 0, 0.8);
}

.todo-ul {
  padding: 0;
}

.stack-vertical {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

@media screen and (max-width: 600px) {
  .App {
    width: 80%;
  }
  .form label {
    display: block;
  }
  .form input {
    max-width: 70%;
  }
}

@media screen and (min-width: 1200px) {
  .App {
    width: 40%;
  }
}