The show has some positive messages for tweens about facing challenges, putting others' needs before your own, and finding common ground with a diverse set of peers. A strong female lead heads up the well-meaning trio.
Multiple violent exchanges in each episode, including guns and heavy artillery (tanks, bombs, etc.). Some of the alien invaders use blasts of fire to level whole sections of a city. But despite it all, actual injuries to humans usually aren't shown.
Some flirting between teens, and girls swooning over cute guys. Occasional brief scenes of teens kissing.