Nice job! reminds me a bit of Mine Sweeper :D.
Took me a couple of fails on easy mode before i noticed the light :D.
Managed to get through easy using the light several times. Then medium mode i focused hard and watched half the board a time. Then on hard mode i suddenly realised it was now easier to just look for where the gold IS, rather then where it isn't :). Managed to get through with a couple of little mishaps.
Fun mini game, well done. :)