Marble Coaster Launcher

This Thing is the 3D-printable body of a spring-loaded ball launcher which launches a 1" ball in a marble run or marble coaster. The front of the launcher is designed to securely hold 1/4" (outside diameter) polyethylene tubing which serves as rails for guiding a 1"-diameter marble along the track. The tubing just snaps into place. I use tubing from Lowe's:
https://www.lowes.com/pd/EZ-FLO-0-170-in-Inner-Diameter-x-150-ft-Polyethylene-Tubing/1000365053
or
https://www.lowes.com/pd/EZ-FLO-0-170-in-Inner-Diameter-x-25-ft-Polyethylene-Tubing/1000180489

Although I imagine any 1" ball will work, the ball I use in my marble coasters is a 1"-diameter solid plastic ball from Pasco Scientific (comes with their physics projectile launcher). They can be bought from Pasco in packs of ten:
https://www.pasco.com/products/lab-supplies/other/me-6822

This launcher was designed to use a spring from a "Master Plumber" brand toilet paper roll holder available at True Value hardware store:
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