Nice game!
PS: How do you make it to have always the same screen ratio in Unity?
Thank you!
For the question: It's likely you already found the answer, but for anyone else:
You can set supported aspect ratios in Unity resolution settings https://docs.unity3d.com/Manual/class-PlayerSettingsStandalone.html
And a way to do it for browser builds is to use this great template: https://seansleblanc.itch.io/better-minimal-webgl-template