Here's how I usually like to go about lasers. You can play with those values to change the maximum range and precision.
It's a good idea to change the 'obstacle' object reference into a family reference (e.g. 'LaserBlocking' so you can have multiple objects block the laser, but I wasn't sure if you had the free edition).
I have no idea why it was over 30mb, that was really weird. I saved it as a project folder, then saved that as a capx, and that fixed it. Very odd.