Swapping
Drag a block to swap it with its neighbour. You swap sideways only, the original Panel de Pon rule. A few effects, like the Ginnungagap Shard's Void window, open vertical swaps for a while and let you build chains you otherwise couldn't reach.
In detail
Swaps are horizontal only by default. Some effects open any-direction swapping for a window and restore the default when it expires. The starting mode is a project setting and can be changed from the dev menu.
More in glossary
From the current development build. Content and balance may change before release. This public reference includes discoveries and does not reflect your personal unlocks.