KOI doesn't have a changeable difficulty setting and, as such, it simply is what it is. Initially, it is a very easy game, only requiring you to move your little fish around and avoid the big black fish. Soon, you'll enter more dangerous areas where there are electrical wires that can stun you and areas that are blocked off by mechanisms until you find the correct fish/flower combos to open them.
Probably the most frustrating aspect of KOI are the puzzles, though. One such puzzle involved leaves on tree branches that would light up in a pattern for you to replicate a la Simple Simon. This puzzle actually had me stumped for a bit because using the stick to move the highlight to different leaves is done in a left to right pattern and not using the full abilities of the Left Stick, as you would control the fish. Since it always seemed to end the pattern by starting on one certain leaf and I was trying to select the leaf below it (not to the left or right of it), at first, I couldn't get the highlighted leaf to change. I can see this frustrating children, who might be drawn in by the simple and pretty aesthetics. As an adult, I was frustrated for a time.
Another puzzle involved matching two chameleons from a group of 8 or 10 in a memory-type game, but it was odd because when I encountered the puzzle and pressed the (Circle) button to activate it, there were no instructions; the timer just started counting down. I assumed it was a color/pattern matching game, but it was tricky, only wanting you to match patterns regardless of the color. The instructions came after I failed to complete the mini-game, but were unnecessarily frustrating.
Finally, the second to last level finds you swimming in a huge lake (much more large in explorable scale than any previous level), populated by stationary little white fish and large hunting black fish, looking to slam into you. I explored the entire area trying to figure out what I was supposed to do, completely stumped and confused. Finally, I realized that the purpose of this level was to get hit a certain number of times by the black fish. What??? This is completely opposite to what the game has taught me the whole way through and I didn't think it was a good way to flip the script.
One more thing - sometimes I'd approach the end of a level, but not realize it was the end of the level, only to see a puzzle piece or star and have the level end on me without having had the opportunity to snag it. Not cool. Sure, I could replay the entire level to grab that one piece, but nah. I think nearly all of KOI's difficulty lies in wonky puzzles and intentionally backwards mechanics.
