How to Fix Knockback Direction from the Wrong Reference Point in GameMaker

An enemy that flies the wrong way when hit has its knockback angle computed from the wrong points or with swapped arguments. Using point_direction from attacker to target fixes it. Here is how.

How to fix it

1. Use point_direction attacker to target

Compute var dir = point_direction(attacker.x, attacker.y, x, y); inside the target so it is pushed directly away from the source. Swapping the argument pairs reverses the direction.

2. Apply force with lengthdir

Set hspeed += lengthdir_x(force, dir); and vspeed += lengthdir_y(force, dir); so the knockback respects GameMaker's angle convention and downward y axis.

3. Reset speed for consistency

If you want the same knockback regardless of prior motion, zero hspeed and vspeed before applying the impulse so existing momentum does not skew the result.

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 GameMaker 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.