I have been working on a mini campaign for minecraft called Jailbreak. and I wanted it to be more than a plain find this this and this adventure, so I've started adding in some mechanics to make it a little more interesting, this is the one i recently just finished after about 2 hours of getting the hang of redstone mechanics and Sticky pistons. I used sand as the platform because i couldn't cover the redstone from the lava without leaving a clear path to the other side out of something, so i had to use 2 sticky pistons on top of each other, which the top won't pull down the block on top of it so sand or gravel was my only actual choice.