Basic steps to earn the secret achievements in Carto. This is not a walkthrough of the main game.
These 10 achievements are earned for completing the 10 chapters of the game and are not missable:
- Set Sail - Finish Chapter 1.
- Horti-carto-ralist - Finish Chapter 2.
- New Growth - Finish Chapter 3.
- Quick Learner - Finish Chapter 4.
- Slaked - Finish Chapter 5.
- One With the Woods - Finish Chapter 6.
- Volcanographer - Finish Chapter 7.
- First Fishtival - Finish Chapter 8.
- Truest Treasure - Finish Chapter 9.
- The Little Cartographer - Finish Chapter 10.
Ground of Applause - Towards the end of chapter 2, you will have a cutscene where you have dinner and clap. A potted plant in the upper right of the cutscene will sway back and forth. After you wake up and go back outside, go to this same plant and press your action button 3-4 times. You'll clap to the plant some more and it will grow a red flower.
Not So Sharp - Touch a bunch of cacti in chapter 4. Around 10 or so.
Cawtet - Chapter 6, there will be 4 birds in 4 corners of 4 map pieces. Place them all together and go to that spot. See image for which 4 pieces and how to align them.
Stirring Things Up - Towards the end of chapter 7, you will erupt the volcano. After this happens, go to the surface and enter the map interface. Interact with the volcano (the plus-sign shaped tile) and spin the tile a few times until the achievement triggers.
Strange Catch - In chapter 8, when you are in the fishing competition, create a fish that is just the head + tail and catch the fish.
Frosty Friend - In the middle of chapter 9, if you fully search every nook and cranny of the map pieces, find a snowman's head, branches, and hat. They are all near the base camp; the hat is the trickiest one to find, as you have to do some manipulation on the ice sliding puzzles... the hat is on the last piece of sliding ice you find. After finding all 3, you'll then find a snowball. Interact with the snowball to build the snowman and get the achievement.
Home Sweet Home - After collecting all 6 of the above pieces/achievements, go to the Secrets option from the main menu. It will unlock the Airship and award this achievement.
Voracious Reader - Read EVERY story in the Story Chalet. This triggered in Chapter 10 for me on my casual playthrough. I was very careful to read every story in every room, every time I was taken back to the Chalet. I also made sure to read the meta-story book on the entrance table at every opportunity, usually multiple times during each visit.
Towering Intellect - Finish the 3 Tower of Hanoi puzzles in the fewest steps possible. This takes place at the beginning of chapter 8. First puzzle can be done in 3 steps, second puzzle in 15, and third puzzle in 1. Steps for puzzle 2: move S-2, M-3, S-3, L-2, S-1, M-2, S-2, XL-3, S-3, M-1, S-1, L-3, S-2, M-3, S-3. Those are listed in Size-Mat format.
Master Cartographer - Complete the game 100%. This should trigger at the same time as the last other achievement you earn. For me, it triggered instantly with Towering Intellect.