I do not understand why you have a free browser game that you must pay for to play on pc. if you can bay for it on the browser i bet you can buy it on steam. i suggest that you either get rid of the browser version or make it like mobile where you can just watch on ad. There are plenty of those.
After the amount of work, time, and effort put into porting it from Flash to Unity, it won’t be going away anytime soon. The Developers have also stated as such; Browser will be sticking around.