So great job on the plugin works really well, only thing I wish it had was the ability to control the transition.
In the old chartboost plugin that was on github it does a slide in from left and the slide out from left, the gremlin plugin slides in from left then “attempts” a peel off to the right slide which doesn’t look that great.
Would be nice to just add in a option for animation = “slideRight” etc. and so forth.
Also and not really a problem with your plugin as it is with chartboost in general is that the close button is always off in space in the upper right.