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You need to detect when the button [color = red]becomes[/color] pressed rather than when it [color = red]is[/color] pressed
See the StateChangeDetection example in the IDE
That will show you how to count how many times a button has been pressed. From that you can work out whether the associated LED should be on or off. On for odd numbers and off for even numbers, for instance
To scale the sketch up to using more buttons then arrays would be useful
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