basically liaunchengs idea a little reworked:
you click the obelisk, which you get to control. the obelisk has a skill named "begin puzzle" or something lile that, so it doesnt appear randomly or unexpected.
you use that skill and wisps appear, lets say like 30 or so, multi-colored.
on top of the obelisk there is a colored wisp. you must click on the wisps with the same color as that wisp to make them disappear. if you click on a wrong one, he doesnt disappear but a new wisp appears. if there are more than Y (say 50) wisps, you lose. every 6 seconds, a new wisp spawns automatically.
the color of the wisp on top of the obelisk changes every 3 or 4 seconds, so you have to be careful not to keep clicking the red wisps when you actually should click the green ones now.
also there are black wisps you never have to click, but if you do, they spawn 5 new wisps.
you could also add row-bonuses. for example, every 3 seconds the color changes. so if you can click 5 red wisps within those 3 seconds, you get a red-wisp bonus.
different bonuses could be:
red wisp bonus: your clicks become AoE-clicks. if you make a wisp disappear, all wisps of the same color around it disappear too (relatively small aoe)
blue wisp bonus: wisps move slower
orange wisp bonus: wisps move faster, but if you make a wisp disappear, another wisp near it changes its color to the color of the disappeared wisp so that you can chain-click many wisps really fast if your accuraccy is good
green wisp bonus: disappearing wisps explode, stunning all wisps around them for a short time (1 sec maybe)
purple wisp bonus: doubles the spawn rate of wisps. i.e. a new wisp spawns every 3 seconds instead of every 6 and if you click on a wrong or black wisp, 2 or 10 wisps spawn instead of 1 or 5.
all bonuses last for 5 seconds.
oh, and the puzzle shouldnt have a timer