How to Fix RTS Box Select Grabbing Enemy Units in Unity

A drag-select that scoops up enemy and neutral units makes group commands behave unpredictably. The fix is to gate each candidate on ownership and a selectable flag before adding it. Here is how to do it cleanly.

How to fix it

1. Project units into screen space

Convert each unit's world position with Camera.main.WorldToScreenPoint and test whether it falls inside the normalized drag rectangle. Skip anything behind the camera (z < 0).

2. Gate on ownership and selectability

Before adding a hit to the selection, require a Selectable component whose OwnerId equals the local player and whose IsSelectable flag is true. Enemy and neutral units fail this check and are excluded.

3. Support modifier keys

Treat Shift as additive and Ctrl as subtractive so players can refine a selection without it silently including hostile units. Clear the set on a plain drag.

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 Unity 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.