What causes a Sokoban player pushing two crates at once?

The push logic only checks that the cell in front of the player holds a crate, not whether the cell behind that crate is free, so the player can push a crate into another crate.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix a Sokoban Player Pushing Two Crates at Once

Quick answer: Before moving, verify the cell directly behind the target crate is empty floor (not a wall or another crate); only then move both the crate and the player.

In classic Sokoban you can never push two boxes in a row. If your player shoves a stack of crates, your push check stops at the first crate and never inspects the cell it would be pushed into. Add that second check.

How to fix it

1. Check the cell behind the crate

When the player moves toward a crate at (x+dx, y+dy), inspect (x+2*dx, y+2*dy). Allow the push only if that cell is empty floor or a goal tile.

2. Reject pushes into walls or crates

If the cell behind the crate is a wall or holds another crate, cancel the move entirely. The player stays put and nothing shifts.

3. Move crate then player atomically

When the push is legal, update the crate's position first, then the player's, in the same step so the two never occupy the same cell mid-move.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Pygame error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.