It is not mandatory  and you can just jump straight to the game if you have prior experience , but I get the feeling that what may seem a balanced difficulty for me will be almost impossible for those who doesn't play games as much.

And I think it's better to inform the players how to play .. than making them learn through trial and error and quit without having the intended experience.(since the gameplay is short)

Yea, some game do require a little explanation. One way to handle it is a simple static screen with controls and maybe a short explanation of the mechanic.

If that’s not enough an optional tutorial is fine, though that suggests that the core mechanic may be too complicated

Or you could show the controls in the game while the player is playing it. If it's not too intrusive this helps the player because they can simultaneously see the controls and try them out. This can be as simple as having a little line of text near the top or bottom of the screen or you can do more fancy if you want to.