itch.io

If you have a lot of textures in the game did you check their size? You can save space by reducing it, although it will reduce also the quality of the images (a bit). See the image below (right bottom, Max Size).

Or you can make LODs: see Pete Jepson's tutorial on Youtube

If you used the Unity engine you can make a build of your game, then, in the console (top right corner) pull down the menu and select "open Editor Log". Scroll down to the section "Complete build size" and you can see how much space every one of your assets takes in your game. You can then optimize the biggest ones.