Square-1: the Vandenbergh method
Cube shape, orientation, permutation, parity.
The Square-1 changes shape as it turns: each layer is a ring of edges and corners (a corner as wide as a pair of edges), and a slice turn swaps half of the top layer with half of the bottom. The Vandenbergh method first restores the cube shape, then sorts each layer's corners and edges (orientation), then puts them in place (permutation), fixing a parity if it is left.
Notation (WCA): (a,b) turns the top a twelfths of a turn clockwise seen from above and the bottom b clockwise seen from below; / turns the right half a half turn. A / is only possible when no corner straddles the cut; the engine refuses any other.
Cube shape: both layers square, seen from above and (turned over) from below.
After a few slices the layers change shape.
(1,0) / (3,0) /
CS
154 cases · Return both layers to squares from any shape: 154 cases.
Reduced CS
11 cases · Cube shape from the shapes with both layers alike: 11 cases.
CO
7 cases · Gather each layer's corners: 7 cases.
EO
7 cases · Gather each layer's edges: 7 cases.
CP
8 cases · Put the corners in place: 8 cases.
EP
49 cases · Put the edges in place: 49 cases.
2-look EP
18 cases · Edge permutation from a smaller set of layer cases: 18 cases.
EPP
50 cases · The parity edge cases, in one algorithm: 50 cases.
Parity
5 cases · Fix the swap the other steps cannot: 5 cases.