Need advice on Android app design. What well? What is wrong?

Question

Android

I am making an android app. Made a design.
As a designer, I am not strong,
so I need advice from those who have already been involved in application development.
Maybe some suggestions, advice?
I will be grateful!
Main menu:

Drawing area:

Drawing area (landscape):

Answer 1

In my opinion, Google has already told everything: https://www.google.com/design/spec/material-design...

Answer 2

The main question for the author of the game application:
How to play it and what is the ultimate goal of the game?!

Answer 3

It really depends on who the app is for and how people are supposed to use it.
From the base:
1. On the main menu, the yellow text on the purple buttons is difficult to read, the italic font also does not add readability.
2. There is a huge empty space on the drawing field, not used in any way. You can place hints there to help the user start interacting with the application.