Diagonal movement

Letting the player (and the joystick) move diagonally — up-left, down-right and so on — instead of only up, down, left and right.

Why not: The game is four-direction by design, and everything that reads a direction is built on that:

• Interaction is four-way. A sign, a chest or an NPC is interacted with from the tile the player faces, and DEFAULT_INTERACTABLE_DIRECTION_MAP lists only the four sides — a player left facing a diagonal could interact with nothing.
• NPCs turn and animate four ways. Talking to an NPC turns it to face the player (getOppositeDirection), and every NPC's walking animation has only the four rows.
• Corners would be cut. A diagonal step checks only the tile it lands on, so the player could slip between two wall tiles that touch at a corner.
• The joystick feels worse. Eight sectors make a thumb that is slightly off-axis walk diagonally, where four snap it to the direction meant.

So the input maps one key to one direction (getDirectionFromCursorKeys) and grid-engine runs with NumberOfDirections.FOUR.