let decks = [
  { name: 'Basic Set'
  , pairs: [
    [ 'hello', 'world' ],
  ]},
  { name: 'Medium Set'
  , pairs: [
    [ 'greetings', 'world' ],
    [ 'bonjour', 'world' ],
  ]},
  { name: 'Advanced Set'
  , pairs: [
    [ 'salutations', 'world' ],
    [ 'aloha', 'world' ],
    [ 'zuzu', 'world' ],
  ]},
];