So, the lootlocker is sponsor of the jam. but, Am i obligated to make a game using lootlocker? like will I be disqualified from the game jam?
No, you can create it with any tool (or use your own) and you can even use an offline leaderboard.
offline leaderboard? Does that can include only high score system? I mean to only show your best instead of other people’s best?
Yep, no problem about that. The bare minimum is that a streamer can compare his scores against previous runs by themselves and others.
