As you make your way through the Macalania Woods, you will run into a NPC who introduces you to the Butterfly Catcher minigame. Whenever you touch the rainbow butterfly on two screens, a bunch of other butterflies will appear, red and blue in color. Your goal is to navigate your way past the red butterflies and touch the blue ones. There are seven blue butterflies to grab and if you are successful before the timer reaches zero, then you will be rewarded with a prize. For every red butterfly you touch, though, you will be forced into a battle with stronger than normal fiends from the area.
Also, touching a red butterfly will make you lose some time, since Tidus will bend down a little bit before the battle is forced on you. If you fail the minigame, then you will need to exit the area and re-enter in order to start it again. There are two screens with this minigame and you will have to complete both in order to get the ultimate prize, the Saturn Sigil. Note that the Sigil is only available once you get the airship, so doing the minigame before then will get you lesser prizes. Also, all random encounters during the minigame are gone, and you will need to make sure not to leave the area after collecting all of the blue butterflies, or else you have to redo it.
The two screens are pretty self-explanatory, although there is a tricky blue butterfly in Macalania North. Whenever you collect the first blue butterfly, which will be right next to where you start, another one will appear just north of it. So, you will have to backtrack to collect that one before setting on the normal path. Also, red butterflies can sometimes be hard to see and more will spawn as you collect the blue butterflies. It will take you a few tries to get it down, but it’s not too difficult of a minigame. You know you failed whenever you’re placed back at the start, while completing it will let you continue running around.