Work backward from the target before pressing any operation. The last move tells you which number you need immediately beforehand, making it easier to plan a short sequence of +2, −2, ×2 and ÷2. The developer's stated goal is to transform the starting number into the target within 20 seconds.
Official game and confirmed rules
Play the free browser game. Its official title is Plus2Minus2 (20sec). Published October 25, 2026 at 10:03 UTC and updated at 10:06 UTC, it is currently labelled in development. The developer lists four operations: add two, subtract two, divide by two and multiply by two. It is entered in 20 Second Game Jam 2026.
Plan a run from start to finish
- Read the starting value and target. The public description does not list keyboard bindings, so follow the controls displayed in the game.
- Check one-move answers. From 6 to 8, +2 is enough.
- Check two-move answers. From 3 to 8, use 3→6 (×2)→8 (+2).
- If neither works, reverse the final move. To end at 12, the previous value could be 10 before +2, 14 before −2, 6 before ×2 or 24 before ÷2.
- Execute your planned sequence and check the number after each move. Reach the target before the timer runs out.
Reverse the final operation
| Final move | Previous value for target T | Restriction |
|---|---|---|
| +2 | T−2 | Addition |
| −2 | T+2 | Subtraction |
| ×2 | T÷2 | T must be even if only integers are used |
| ÷2 | 2T | Previous value is even |
For example, 7→14 (×2)→12 (−2) and 8→6 (−2)→3 (÷2) each take two steps. These are valid arithmetic examples, not levels observed during a completed game session.
Odd and even numbers
Adding or subtracting two preserves parity. Multiplying by two produces an even number. If exact integer division is allowed, 6÷2=3 is a way to obtain an odd number from an even one. A possible route from 6 to 7 is 6→3 (÷2)→5 (+2)→7 (+2). The developer has not documented rounding for odd-number division, negative values or whether puzzles are randomized.
Common mistakes and FAQ
| Problem | Better approach |
|---|---|
| Repeated +2 takes too long | Look for doubling followed by a ±2 correction |
| Doubling overshoots by two | Follow it with −2 |
| You need an odd result from an even start | Look for an even value whose half is odd |
| Division would create a fraction | Start with exactly divisible numbers until the rule is clear |
Is there a universal winning sequence? No fixed solution is published; check one and two moves before working backward. What score wins? The stated objective is matching the target, not a documented score threshold. Which keys? The listing does not specify bindings.
Conclusion and sources
Choose the final move first, then make the opening move. A 20-second maths challenge is a surprisingly good place to think in reverse.
Sources: official game and release details, jam rules. Checked October 25, 2026 JST. No hands-on completed run; exact controls, division rounding, social engagement and the developer's X post remain unverified.
