Briefing
The Festival Goes Dark
Principal Nezu was found unconscious in the development lab last night, hours before the Inter-Academy Crossover Festival showcase. His prototype invention — the one he was due to unveil on stage — is gone.
Eight students were in the building that night. Each decoded clue reveals one trait of whoever's responsible — age, hair colour, gender, anime — and you'll need to cross-reference every one against the suspect board.
Your job: decode the evidence, narrow the suspects, and crack the case before the showcase opens.
Suspect Board
Eight Names, One Night
Each decoded clue reveals one attribute of the culprit. Check it against the cards below and rule out anyone who doesn't match. Click a card to mark it ruled out, click again to bring it back — your choices are saved automatically.
Evidence 1 · A Scorched Fragment
What Was Left Behind
Tucked under a workbench in the lab, you find a strip of paper with a pattern of binary digits — the same code Nezu uses in his private notes. Each group is 5 bits. The place values (16/8/4/2/1) are shown above each group — add up the ones switched on to get a number from 1–26, then turn that number into a letter (1=A ... 26=Z).
Show me how ▸
Evidence 2 · The Keycard Log
Bigger Numbers, Same Idea
Among the wreckage, a torn keycard log shows a string of binary. This time it's full 8-bit ASCII — same idea, bigger place values (128 down to 1), shown above each group. Use the ASCII chart in the decoder if you need it.
Evidence 3 · No Gaps This Time
Find Your Own Boundaries
This one's trickier. The numbers were copied in a hurry — there are no gaps between the bytes, and no place values shown above them either. Still 8 bits per letter. The next letter always starts right where the last one finished (look for the highlighted bit) — click where you think it ends and lock it in once you've got exactly 8. Each byte you lock gets its own box above — work out that letter before moving on to the next one.
Evidence 4 · The Note
Real ASCII
Folded inside a locker, a short note in proper text — capitals, lowercase, even punctuation. This is the same encoding scheme real computers use for text, so case matters here: a capital letter and its lowercase version have different ASCII codes.
The Vault
Ten Rounds, Fast
Behind a false panel in the lab: a vault locked with ten rounds of binary. Press Start once and the switches check themselves — match a target and it moves straight on to the next one. Run out of time on any round and it's back to round 1. Crack all ten in one run and a bonus file unlocks with one more clue.
Solve the Case
Who's Responsible?
You've got the evidence. Who's responsible for what happened to Principal Nezu?
For Teachers
Teacher Notes
Learning objectives
- Convert binary to denary using place values
- Map denary values to letters via A1Z26 and via ASCII
- Understand why text encoding uses a fixed bit-width (8 bits) and why byte boundaries matter
- Recognise that uppercase and lowercase letters have different ASCII codes
- Use process of elimination against a data table — each clue narrows 8 suspects down by one attribute at a time
Suggested timing (50–60 min lesson)
- 5 min — Briefing + suspect board read-through
- 10 min — Evidence 1 (worked example, whole class together)
- 10 min — Evidence 2 (independent/paired)
- 10 min — Evidence 3 (independent, expect some retries — this is the point)
- 10 min — Evidence 4 (independent/paired)
- 10 min — The Vault + Solve the Case, then whole-class debrief
The deduction chain
Evidence 1 (gender = male) narrows 8 suspects to 6. Evidence 2 (hair colour = black) narrows 6 to 4. Evidence 3 (age = fifteen) narrows 4 to 2. Evidence 4 (anime = Jujutsu Kaisen) narrows 2 to 1. The Vault's bonus file (signature move = Shikigami Summons) is a deliberate double-check rather than a fifth load-bearing clue — by that point pupils should already be at one suspect, so it's reinforcement, not new deduction. Pupils who decode correctly but skip the suspect board will miss this — it's worth explicitly prompting them back to it after each Evidence screen.
Why Evidence 3 has no gaps (or place values)
Evidence 3 deliberately removes both the byte boundaries and the place-value labels that Evidence 1 and 2 give for free. The next letter always starts exactly where the last one ended (the tool fixes that point for you, so pupils can't accidentally lock in a byte that starts in the wrong place) — the only thing left for pupils to work out is where each letter ends, which still requires them to understand that every letter is a fixed 8 bits wide and count accurately to find it.
Differentiation built in
- The decoder helper is always visible alongside each Evidence screen — no extra click required, and it sticks in view while scrolling
- The Vault's timer can be switched off per pupil/device without losing the activity — this matters more now, since timing out on any round sends the whole run back to round 1
- The Vault's bonus decode reinforces the final attribute (Signature Move) rather than just being a timed mini-game with no payoff — pupils get one more piece of evidence, not just a score
- This page has no visible link — type the word "teacher" anywhere on the page (no need to click into a box first) to reopen it
Answer key (click to reveal)
| Evidence 1 | MALE |
| Evidence 2 | BLACK |
| Evidence 3 | FIFTEEN |
| Evidence 4 | Jujutsu Kaisen. |
| Vault targets | 154, 23, 7, 200, 91, 250, 64, 233, 100, 175 |
| Vault bonus clue | SHIKIGAMI (Signature Move) |
| Culprit | Megumi Fushiguro |