Thank you very much for your question!
This is a little detail that often causes some confusion for Spanish learners! We have a brief explanation on using jugar
"to play" with or without the preposition a
and a definite article in Level 2, Lesson 9.7, which I will copy here:
Note that using jugar "to play" with the preposition a "at / to" and the definite article ("the") when talking about games and sports is standard Spanish. However, you'll hear many Spanish speakers in Latin America drop the a and the article before the game/sport when speaking colloquially.
The conversation in Level 1, Lesson 5.3 is very colloquial, and so it uses jugar
and a preposition. Literal translations are provided in our courses where jugar
is used with a
and a preposition to try to make this clear in the Reinforcement activities, but I will ask the Spanish team if they can look into making this difference more obvious in some way.
I hope that this is helpful! Do let me know if you still have any questions.