OPAL puzzle hunt public archive
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. Partial answer confirmation not supported.
OPAL 2: Museum of OTIS Things#
OPAL 2 started on September 5, 2025.
- patri〇TISm, by Evan Chen
- Sine, by Evan Chen
- Flower, by Evan Chen
- Word Search, by Abel George Mathew, Evan Chen, and Manu Param
- … for now, just the first four puzzles are uploaded. The rest will be uploaded later. (If you don’t want to wait, email me and I can send you the rest.)
OPAL 1: Alice in OTISLand#
OPAL 1 started on August 30, 2024.
- Plot, by Evan Chen
- Binary, by Evan Chen
- elemeNT, by Rachel Chen, Rohan Garg, Sean Yeh
- eIGen-bIGrams, by Evan Chen
- Learn to Code, by Evan Chen
- Diagramless Crossword, by Calvin Wang and Royce Yao
- Steam, by Evan Chen
- Catalog, by Evan Chen
- Last Layer Magic, by Ethan Lee
- Digitized, by Jiya Dani and Charles Zhang
- r/AnarchyChess, by Arul Kolla
- Operators, by Elijah Liu
- Alice in OTISLand (meta), by Evan Chen
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Stands for OTIS Puzzle Assembly Line. ↩
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The live website will track your progress, provide pre-written hints, and grant rewards on completing the metapuzzle. ↩
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In particular, puzzles might expect solvers to know about OTIS-related things; for example, one puzzle references a problem on the OTIS application. Other puzzles may assume other data specific to OTIS. All needed information needed is publicly available (e.g. in the OTIS syllabus), but you may have to know to look for it. ↩