Why are all the police, firemen, and nuns after Grandma? WHAT HAS SHE DONE!? Some extra back story that Grandma was a spy or criminal mastermind or something would be useful...
It did pause a bit on the web loading the effect for the attack, so that confused me a bit at first. I was also hoping to advance the dialog with the keyboard (space), it was weird to have to go to the mouse just for that when the main controls are keyboard. You could also have mouse control for movement and attacking as well to just allow both.
This was definitely quite the escort mission of a game. There didn't seem to be any consequences though, I was expecting to lose if someone reached grandma or for her to have a health bar or something at some point. I did like that there was the range where she would follow you, leaving her to fight off the swarm felt like an interesting choice, but it'd be nice to have a bit more substance and stakes in the fight.