Very simple, an easy creation of mine (@MasterAndras). You can change the variable Angle. It will stop increasing in size after it reaches a certain size so you can restart if that happens. Use the Space bar to clear and start again. Be sure to try adjust Angle to these values: 2-5, 8-14, 20, 45, 70, 90, 100 however you can try any value you like! Be sure to leave any comments or remixes on how to make this a better project (even though this was just a quick project LOL)!
Creds: @MasterAndras for original project Some very simple corrections by me. First: It stops cloning because Scratch only allows 300 clones on screen. Therefore I have used the stamp block instead. New in v1.1: Added space bar that can clear and start again. Added System Chat that reminds you when it is at it's maximum size. Made the 'thing' in the middle spin slower as it will sometimes crash the simulation. However the speed still varies from time to time. Sorry.