This Seeking Tech guide will show how you can unlock the Hidden Game trophy and achievement in Final Fantasy I Pixel Remaster.
1. If you haven’t done so already, make sure you progress enough through the story until you get a ship.
2. Next, you need to enter the ship.
3. Afterwards, hold down on the Confirm button and then rapidly tab the Back/Cancel button.
Since I am playing with a PlayStation controller, I held the X button down while rapidly pressing the Circle button.
4. After around 72 presses of the Back/Cancel button, then you should see a pop-up notification asking if you want to play 15 Puzzle.
5. Select Yes to play the mini-game and you should unlock the Hidden Game trophy and achievement.
You don’t need to complete the sliding puzzle as it won’t give you any other rewards.