In OTIS, the OPAL hunt¹ is an annual one-round beginner-level puzzle hunt hosted for OTIS students. This page is a public archive of past OPAL puzzles. Current or past otters should solve on OTIS-WEB, not here.²

Because of the audience, there’s a lot of math and OTIS references³. I don’t have solutions, but you can email me with hint requests.

Static answer checker#

The static checker above can be used to check a final answer to any OPAL puzzle. A few puzzles will also confirm partial answers if you’re close (the checker will say “keep going!” instead of just “incorrect”).

OPAL 2: Museum of OTIS Things#

OPAL 2 started on September 5, 2025.

1. patri〇TISm, by Evan Chen
2. Sine, by Evan Chen
3. Flower, by Evan Chen
4. Word Search, by Abel George Mathew, Evan Chen, and Manu Param
5. Protoss Cookbook, by Evan Chen
6. The Menu, by Calvin Wang
7. Chain, by Evan Chen
8. Forged Under Pressure, by Žiga Oštir
9. Bitstream Player, by Evan Chen
10. Conundrum, by Evan Chen and Patrick Du
11. Function Composition, by Jason Mao
12. The Great Debate, by Calvin Wang and Patrick Du
13. Cryptanalysis, by Evan Chen
14. OTIS Art Gallery Problem (meta), by Elaine Hou and Evan Chen

OPAL 1: Alice in OTISLand#

OPAL 1 started on August 30, 2024.

1. Plot, by Evan Chen
2. Binary, by Evan Chen
3. elemeNT, by Rachel Chen, Rohan Garg, Sean Yeh
4. eIGen-bIGrams, by Evan Chen
5. Learn to Code, by Evan Chen
6. Diagramless Crossword, by Calvin Wang and Royce Yao
7. Steam, by Evan Chen
8. Catalog, by Evan Chen
9. Last Layer Magic, by Ethan Lee
10. Digitized, by Jiya Dani and Charles Zhang
11. r/AnarchyChess, by Arul Kolla
12. Operators, by Elijah Liu
13. Alice in OTISLand (meta), by Evan Chen