What is the best way to represent the difficulty level in a children's game?

I am building a game for children.

The game contains questions.

Age range: 5-18.

Context: learning.

Before the questions I have a screen where the children select a difficulty level:

I want to replace the text "Level.." with somthing else which is not textual language.

I thought about colors or symbols. What is the best user experience for kids?

Answer

You could use several cues to reinforce each other: Background getting slightly darker at more difficulty. Use a star - which is a positive symbol, whatever the difficulty. Use more of the stars for more difficult levels Use colours for the stars.

For example: