How do I aim and fire at the same time using my Magic Mouse or Trackpad?
If you are using a Magic Mouse or Trackpad, you cannot click the Left Mouse button while holding down the Right Mouse button. This means that you cannot aim and fire using only your mouse.
Instead, you can aim by holding down the Alt/Option (⌥) key. You'll then be able to fire using the Left Mouse button as normal.
If you prefer, you can change the key bindings for aiming and firing. You can customize your keyboard configuration by selecting Options → Mouse & Keyboard → Keybindings from the Main Menu.