+- **The 2nd instance is visible but stuck on the loading screen — and only advances
+ when you jiggle the mouse.** Root cause: BL2's `bPauseOnLossOfFocus=TRUE` — the
+ game **pauses itself whenever its window isn't focused**. In split-screen only one
+ window is focused at a time, so the unfocused instance freezes until an input event
+ wakes it. `setup`/`run` patch each prefix's `WillowEngine.ini` to
+ `bPauseOnLossOfFocus=FALSE` so every instance keeps running unfocused. (This was
+ *not* CPU scaling, entropy, or window occlusion — those were dead ends.) The
+ instances also share a DXVK shader cache so the 2nd reuses the 1st's compiled
+ shaders; `STAGGER=45` further separates their loads if a cold first run is slow.
+- **Two soundtracks at once:** each instance sets `bMuteAudioWhenNotInFocus=TRUE`, so
+ only the focused window plays audio — the sound follows whichever instance you're
+ focused on, instead of both playing together.
+- **In-game "Quit Borderlands 2 → Yes" does nothing / hangs:** the game's shutdown
+ path stalls under Goldberg (Steam-networking cleanup, worse with offline mode).
+ Don't use in-game Quit — close with **`./bl2-splitscreen.sh kill`** or **Ctrl-C**
+ in the run terminal (safe: you're at the menu, nothing is saving).
+- **Ctrl-C / kill left something running:** `./bl2-splitscreen.sh kill` tears down
+ the whole game + Proton/Wine tree.