See the trap demonstrated here. I wonder how much our first grader actually did. But he's smart as a whip so he was probably a consultant who suggested the laser beams. Oh, by the way, the leprechaun is prevented from jumping out by a plexiglass cover which was left off for the demonstration because of the glare.Every year at least one of our grandkids constructs a leprechaun trap (with the help of engineer dad). This year was the most complicated of all.
Frankly, I suspect that the trap will fail because leprechaun's move at lightening speed and have acute hearing so the minute the magnet begins to operate, he'll here it and dash out under the door. (Did the door catch a bit of green cloth from his coat?) Hey, if Indiana Jones can do it, it's a piece of cake (or Irish soda bread) for a leprechaun! Proof for my theory? I'll bet the door was closed and there was no leprechaun in the trap!
Anyway, Happy St. Paddy's Day and I hope you catch a leprechaun, eat some corned beef and cabbage, and wish the top o' the morning to everyone you meet. We are all Irish on St. Patrick's Day, even St. Patrick who was really a Brit.