While this could work, please don’t go firing a laser powerful enough to set shit on fire randomly into the air. It’s like firing a gun, that laser will fuck up whatever it hits and you don’t know what’s behind that flag. Easy way to kill a plane full of people by instantly and permanently blinding both pilots. I would look into artillery calculations and water balloons filled with bleach. Pretty easy to hit a stationary target with a pi handling trajectory calculations. Paintballs might be another option, bright pink.