Is Gwendolin's tutorial mission possible to no-hit?

[Enderspoons]

The first wave always leaks a red and blue bloon through. It doesn't seem like I'm able to do anything to stop them, as I can't build any towers, use any powers, upgrade Gwendolin, or activate the map's crusher.

Am I missing something here?

[Hiroko]

probably positioning and/or target priority
and remember you can also change target priority mid-wave