How to handle letterboxing / black borders on mobile?

Hey folks,

New user to the forum here. I making a little game for mobile, I have been looking it how to adapt it for multiple screen sizes.

The game I’m making is similar to Mike Dangers, where the hero goes from left edge to right edge.
As seen in the screenshot above, there are black bars on left and right of the game on certain devices.

I’m using mobile template provided by Defold, I don’t want to change the projection that stretches my game, I want to main the aspect ratio of my game.

What should I do to utilise the whole space on x-axis and y-axis? Any suggestions.

You should be able to use Fixed or Fixed-Fit projection: