Check these four things first
Is it your turn? Does the move have the correct L-shaped offset? Is a friendly piece on the destination? Would the move leave your king in check? Pieces between the start and finish do not block a knight’s jump.
1. Count from the starting square correctly
A knight on d4 can jump to e6: one file across and two ranks up. It cannot jump to e5, which changes each coordinate by only one. Think of the differences between the two squares rather than drawing a path through neighbouring squares.
From d4, the eight geometric destinations are b3, b5, c2, c6, e2, e6, f3 and f5. Board edges remove destinations that would fall outside a–h or 1–8. The movement guide has a labelled diagram and exercises.
2. Inspect the destination, not the pieces in between
A friendly pawn on f5 prevents your knight on d4 from landing on f5. A pawn on d5 does not prevent a jump to e6. The knight does not need a clear walking route.
In ordinary chess, landing on an enemy piece captures it; jumping over an enemy piece does not. The destination can be occupied by an enemy piece and still be unavailable for another reason, such as leaving your king in check.
3. Is your knight pinned to the king?
Consider the relevant pieces in this diagram: your king on e1, your knight on e2 and an enemy rook on e8. All intervening e-file squares are empty. The diagram isolates the line; it is not a complete starting position.
If the knight leaves e2, the rook’s line to e1 opens. A knight jump cannot remain on the same file to keep that line blocked, and the rook on e8 is not a knight jump away. In this isolated example the knight cannot legally move. This is an absolute pin: the issue is exposing your king, not a piece blocking the knight’s jump.
4. Are you already in check?
A move must answer an existing check. Moving an unrelated knight to a nice attacking square does not solve an attack on the king. Depending on the position, a knight might capture the checking piece or block a sliding piece’s line; it cannot do either just by jumping over the attacker.
Do not use a general checklist as a verdict on an unseen board. Other pieces, a second attack or an occupied destination can change which replies are legal.
5. Separate game rules from app controls
Confirm the selected piece, whose turn it is and whether you are viewing a replay or analysis board. If the position is ordinary chess, compare the move with the app’s legal-move highlighting. An app refusing one move is not by itself proof of a software bug.
Variants may add constraints or change the objective. Check the mode’s rules before applying a standard chess explanation. Our variant comparison links to complete rules for several examples.
What about Knight Chase?
Knight Chase is our separate Android game. Its standard duel has no king to expose, so the pin above is not an explanation for an unavailable Knight Chase move. Instead, check sealed squares, current power-ups, hazards and the highlighted destinations. Adventure objectives can differ from duel rules.
Start with the Knight Chase beginner guide or try the guided trap. For a reusable-square exercise with no king or captures, solve the alternating knight swap puzzle.
Rule checks: FIDE Laws of Chess, Articles 3.1, 3.6 and 3.9. The pin diagram and examples are original AZIN Games teaching positions.