1. Walking through doors is hard, even without staircases: proving PSPACE-hardness via planar assemblies of door gadgets;Ani,2020
2. Pushing blocks via checkable gadgets: PSPACE-completeness of Push-1F and Block/Box Dude;Ani,2022
3. Tracks from hell – when finding a proof may be easier than checking it;Almanza,2018
4. Trainyard is NP-hard;Almanza;Theor. Comp. Sci.,2018