My feedback: Nice game!  It definitely has an addictive aspect to it, with the "just one more try" factor like Flappy Bird and others.  I believe that its gameplay is this game's greatest single strength.

The music soundtrack is effective and consistent with the game's overall look and feel.  The graphics are appealing, and express the Game Jam's theme of "Ruins" well.  I might suggest a couple refinements: the full-screen mode worked great initially, but after pressing <Esc> on my keyboard to exit fullscreen mode, there was no way that I could reactivate fullscreen mode (unless I am overlooking something).  And then I also noticed that in windowed mode, the score would show during the game but the score is omitted or obscured while in fullscreen mode.  This doesn't affect gameplay, but it does affect the user's overall experience of the game.

Nice to see an example of what the BASIC dialect QBJS is capable of in a browser.  I am not familiar with QBJS, but if this game is any indication, it looks like a capable and robust implementation of BASIC judging by this game produced with it.  Thanks for the entry in the Game Jam, and for the inspiration it provides for me to work through and complete my own BASIC language based game projects!