easter egg

test.js

const expected = [
'ArrowUp',
'ArrowDown',
'ArrowUp',
'ArrowDown',
'ArrowLeft',
'ArrowRight',
'ArrowLeft',
'ArrowRight',
'a',
'b',
'a',
'b',
'Enter',
  ]

fromEvent(document, 'keyup')
  .pipe(
    map((e: KeyboardEvent) => e.key),
    bufferCount(expected.length),
    mergeMap(keys =>
      from(keys).pipe(
        sequenceEqual(from(expected))
      )
    )
  )
  .subscribe(e => console.log(`You win!`));