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Thanks Yaz! You're too kind :D
Regarding the size of the file, I do agree with you, it's incredible (I'm surprised myself). Unity is great for optimization (even if not perfect, real programmers still complain). I think it's been thought on purpose because of the compatibility of the engine with smartphones: these games have to be small and optimized.
Also, Boklin is small because there is no texture, no image, no video, on the contrary of some of my other games. Textures and images are what increase the size of the game most. You can see it with Catyph, 2GB of size! Here there's only polygons, colors, text and data. 

When you work with images, you need to optimize them a lot "for the web" (the photoshop feature is good for that). When you save a standard JPG, even with a low quality setting, it will still be bigger than a JPG "saved for web", in which everything is optimized (color palette, level of detail, etc). You have to use all the techniques that exist in order to optimize your games. Using PNG is usually not recommended if you want to lower the size of the game, unless you absolutely need transparency (which can also be avoided with some techniques: I saw it in the Mighty Slot game, he did like me in ASA using no transparency on some buttons/interactive objects that appear of disappear in a cropped area).
If your engine supports it, you can also use "newer" compressions such as webp for pictures and webm or ogg for video and audio, etc. It's always a sacrifice to do and a balance to find between the size of the project and the result in game... And it is way easier with full 3d and no texture than with prerenderend games!