Super cool feel to this - it looks like either the sprites for the crystals don't respawn when I leave the shop or the collision box for the crystals doesn't despawn. I'm able to collect invisible crystals to my hearts delight.
Thanks! We all put a lot of work into it and created all of the graphics and the sound effects/music.
Yes this is an unfortunate bug that was discovered too late. The sprites are hidden but the collision box remains. To play in the 'spirit' of the game, try and avoid collecting already collected crystals.