Since there can be an HTML build, are features that are only on phones like the accelerometer not usable ? And what defines exactly the fact that it's a mobile game except not using a keyboard and a mouse ? I can't wait to participate to this game jam ^^

Go ahead and use any mobile feature that is exclusive to phones! After all, this is the "Mobile Game Jam." Any game that prioritizes its mechanics and design for a mobile device definitely counts as a mobile game. Thanks for joining!