Used in multiple ways...
Show constructions first, have students come up with steps and reasons
Show steps first, have students perform the constructions
Show a couple, then have students try to explore other options, then show solutions.
Lots of possibilities. School internet connection is sometimes not the most reliable, and sometimes sites are blocked, etc...I wanted to have something I could use that was not reliant on having a solid internet connection or 1-to-1 student computers.