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''A Taxonomy'' by David Howe could expand piece-types to 10 or even 20. With planar pieces, conflated with my ''Multi-path'' article(2004) there is a five-Phylum system: Slider, Leaper, Rider, Multi-path, Planar. That works well at least for this comment. People are ignorant of biology's five-Kingdom system: monera, protista, fungi, plantae, animalia, thinking there are only the last two. If planar as type is useful, as with the others, there are overlaps here and there, and they are productive not distracting. L.Smith (another originator of planar is G.Smith) here shows slider interpreted as planar. Still we would tend to keep slider Phylum too for something seeming fundamental about linear sliders especially. Take leaper Flamingo (1,6) variantly defined as requiring set vacancies along both its long columns from departure to arrival, not complete vacancies. That Flamingo, carefully chosen as colourswitching to avoid L.Smith's diagonal planar capability, is synonymous with just ''Planar.'' (Here for convenience we're assuming orthogonal nullification in effect.) So Planar and Leaper blend like Planar and Slider, as Smith incorporates. And Planar overlaps to the same extent with Multi-path, the latter having only specific routes and almost always allowing some occupancy within the rectangular plane from departure to arrival. Especially the Diagonal Planar component and Multipath considerably overlap. In the last paragraphs, when Smith refers to ''playing field,'' he means the intermediate sub-rectangle betwixt. Also in the same sentences, when he writes ''definite steps,'' that's isomorphic with Multipath, the aforementioned shared regions of those 2 of the 5 in the over-all. Since planar, diagonal or orthogonal, boils down to specific pathways, even if requiring all of them, they could all be interpreted as Multi-path. But it could work the opposite way too, Planar encompassing Multi-path. So the specific context steers us to one or the other designation. Each of the five overlap each of the other four in their way and context: think about it, even for the pair Slider and Leaper definitionally. With proliferation, improved classifications are absolutely necessary.
These are all in one Kingdom. The other Kingdom would be pieces and their types that don't move but have effects. What other categories suggested by the Howe article could go within the Kingdom of movers? See follow-up there soon.