"Spaceman" is a more colloquial term that can refer to astronauts or to anyone who travels in space, including cosmonauts (from Russia) and taikonauts (from China). In general, "astronaut" is the more formal and widely recognized term, while "spaceman" is more informal and can be used in a broader sense.

an astronaut (= person who travels into space)

You can invite friends to join your lobby through steam by clicking the "Invite Friends" button around the bottom middle of the screen. A maximum of 4 players and 4 spectators can join the lobby before it is full.

One new mechanic in Blaze is the addition of health bars. In the original Lethal League, one-hit knock-outs were the name of the game. In Blaze, those are only possible when the ball is moving at triple-digit speeds. Any hit from the ball just takes a bit off your health otherwise.