The beauty of playing futsal, which is extremely popular in Brazil, is unlike in indoor soccer, there are no walls to play the soccer ball off of. Instead, in futsal you have to control the soccer ball and keep the ball in bounds just like in outdoor soccer. Christian Pulisic played futsal growing up and he's said it improved his technical ability and soccer skills in tight spaces. In fact, his dad had to start a futsal league in his area just so Pulisic could play it since they didn't have one.
And, in futsal you use a different kind of soccer ball, one that doesn't bounce as much and is a bit smaller and weigher. Overall, futsal is a great way to improve your touch and skill on the soccer ball during the off-season. Since it's a small sized field you can more touches on the ball.
Check out the awesome futsal (indoor-soccer) skills from Ronaldinho in the video below. While this is an older and retired Ronaldinho, you can still see he's got skills on the ball that made him the best player in the world when he played the game.
"A lot of the moves I make originate from futsal. It's played in a very small space, and the ball control is different in futsal. And to this day my ball control is pretty similar to a futsal player's control." - Ronaldinho
Finally, here's a quick overview of futsal. An introductory guide to the rules of futsal, the official FIFA-sanctioned version of small-sided football. It's be nice to see more futsal courts setup in the United States, perhaps smaller versions of the game so young kids can play in city parks.