Speed quiz
Blackout logic puzzle: 16 houses
Every house reports on other houses. A lit house reports truly, a dark house falsely, and a flickering house may do either. Exactly one house in the grid is flickering.
- Format
- Logic grid
- Items
- 16 cells
- Limit
- 8:00
- Level
- Medium
- Checked
- 2026.10.03
The rules as listed below.
- Grid
- 4 by 4, 16 houses to mark
- Time limit
- 8:00
- Checks
- 3
- Press a house to cycle its mark: lit, dark, flickering, then blank again.
- Check the grid once every house is marked. A check says how many are wrong, never which.
- Keyboard: arrow keys move between houses; L, D, K set a mark and Backspace clears it.
- Pause whenever you like (Esc). The board hides while the clock is stopped.
Mark every house lit, dark or flickering. The grid appears when you start.
About this quiz
A three status logic grid. Lit houses tell the truth and dark houses do not, but a flickering house can say anything, so it has to be caught by what the others say about it.
- The number of flickering houses is given with the rules.
- A flickering house's own report proves nothing either way.
- The solution is unique and can be reached without guessing.
More quizzes like this
| No. | Quiz | Section | Format | Items | Added |
|---|---|---|---|---|---|
| 01 | Blackout logic puzzle: 25 houses A power cut on a 5 by 5 street grid of 25 houses. Lit houses report truly, dark houses falsely, flickering ones either way. Work out which is which. Speed / Logic grid / 25 cells | Speed | Logic grid | 25 | 2026.10.03 |
| 02 | True or false logic puzzle: 5 by 5 A 5 by 5 grid of 25 statements about each other. Mark every cell true or false: only one way of doing it holds together. Speed / Logic grid / 25 cells | Speed | Logic grid | 25 | 2026.10.03 |
| 03 | True or false logic puzzle: 4 by 4 A 4 by 4 grid of 16 statements about each other. Mark every cell true or false: only one way of doing it holds together. Speed / Logic grid / 16 cells | Speed | Logic grid | 16 | 2026.10.03 |