New Grid Visibility slider (Options → Accessibility) lets you brighten or fade the board's grid lines, from fully invisible up to twice as bright as before.
New Thick Grid Lines toggle doubles the grid line width, for players who still find it hard to see even at maximum Grid Visibility.
New Ghost Piece Opacity slider lets you adjust how visible the falling piece's landing preview is, from fully invisible to fully opaque.
New Ghost Outline toggle adds a bordered outline around the ghost piece for extra contrast.
A live preview on the Accessibility tab shows the effect of all of the above in real time, without needing to start a battle to check.
New Lock Delay slider (Custom Difficulty) lets you tune how tightly a piece's lock delay is tied to its fall speed, instead of a fixed ratio.
Multiplayer
The Attacker's board now respects your Color Scheme, Grid Visibility, Ghost Piece Opacity, and Thick Grid Lines settings, instead of always using one fixed look with no grid at all. Every color scheme, including the colorblind-safe ones, now has its own matching dark variant on the Attacker's board.