"In Esperanto you can create a new word."

Translation: En Esperanto vi povas krei novan vorton.

[Cambarellus]

"In Esperanto you can create a new word"... but Duolingo will mark you incorrect and tell you to use the real words.

[Ariaflame]

Well, you've got to learn the language before you can hack it. The computer system isn't an AI. It can't tell if you have created a new word that makes sense.

[InoAuxIcxo]

Why would it not be 'per', the 'in' is not literal.

[Vortarulo]

Esperanto isn't 100% logical, it is not Lojban. So "en" can refer not only to spatial concepts (en la domo), but also to temporal ones (en la jaro 2002), and to abstract concepts (en tiu situacio, en Esperanto, en amo).

"Per" works but means something different, more like "by means of".

[JasperJP]

En preskaŭ iu lingvo oni povas krei novajn vortojn :p

[BossLearner87]

You can say "pra" then follow it with "avo" an infinitely different number of times

[mizinamo]

You mean as in praavoavoavo ?