Quick answer: Construct 3 trackpad pinch on macOS firing as mouse wheel events with reversed direction? macOS sends pinch as scroll with ctrl - intercept and convert to your zoom.

Mac users pinch-zoom out; game zooms in. Same gesture on iOS works correctly.

Handle wheel with ctrl

Listen for wheel events with event.ctrlKey. Treat as zoom; sign matches deltaY but you may want to invert for natural feel.

Or use the Pinch behavior

Construct 3's Pinch behavior handles trackpad on supported browsers. Adopt over manual wheel handling.

Block default to prevent page zoom

preventDefault on the wheel event. Without it, the browser zooms the whole page.

“Trackpad gestures map to mouse events. Mouse events with modifiers are how the OS communicates intent.”

Test on a Mac trackpad explicitly. The bug doesn't reproduce on mouse-only setups, so it ships hidden.