How do I optimize size of my unity word puzzle game?

We have developed Word Puzzle Game for android. The size is greater than 20 MB because we have developed game with the help of Unity game engine.

Even blank project will take approx 10 MB for APK in Unity.
Your advise would be helpful.
Thanks in advance!

Try to resize the Tetxure resolution, but i think that you wont get the size much smaller. In my current Project the size of the Assembly C#.dll ( the game code) is 3MB and 1 texture sometimes have 80mb.
So its difficult to get it much smaller! You can also try to lover the Quality at a Audio Import settings.

resize all your sprites with power of two values. (maybe creating logical atlases could help more) this way Unity can compress your visuals better.

also if you dont mind leaving some devices not supported for your game you can decrease supported api level count in build settings.

you can change your audio files from stereo to mono channel.

etc.

You should always start by reading the manual: Unity - Manual: Reducing the file size of your build