Stack-top roads
Build an orthogonal road whose visible top stones belong to one player.
Logic & rule checking
- Players
- 2
- Time
- 15–25 minutes
- Materials
- 3×3 grid; eight flat paper stones per side
Prepare
Start an empty 3×3 board. Each player has eight flat stones marked W or B. A player controls a stack only when its top stone is theirs. A road is an orthogonally connected path of controlled cells joining either pair of opposite board edges.
Play
On a turn either place one reserve stone on an empty cell or move a controlled stack. To move, lift one to three stones from its top, preserving their order; never lift more than the stack contains. Choose one orthogonal direction and distribute the lifted group over one or more consecutive cells in that direction.
Worked example
Drop at least one stone on each visited cell, preserving bottom-to-top order, and finish with none carried. You may land on occupied cells and cover their tops. No turning, off-board step or crossing an unvisited gap is allowed. No standing stones or special pieces exist.
Finish and check
Example: carry top group bottom B,top W from A1. Drop B on B1 and W on C1; those cells’ new tops are B and W. Dropping W first would reverse the lifted order and is illegal. Reserve placement cannot cover an occupied cell.
Adaptation and limits
Check roads after each turn. If both sides have roads, the mover wins. If no road and the board becomes full or either reserve becomes empty, count controlled cells: more wins, equal draws. Otherwise stop at 40 turns as a draw. Record stack contents, not only tops.
Purpose, observation and provenance
Within this activity: Build an orthogonal road whose visible top stones belong to one player.
A partner can replay each legal action and explain the stopping condition; this is an observable task, not evidence of lasting improvement.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Rules to keep beside the materials
- Start an empty 3×3 board. Each player has eight flat stones marked W or B. A player controls a stack only when its top stone is theirs. A road is an orthogonally connected path of controlled cells joining either pair of opposite board edges.
- On a turn either place one reserve stone on an empty cell or move a controlled stack. To move, lift one to three stones from its top, preserving their order; never lift more than the stack contains. Choose one orthogonal direction and distribute the lifted group over one or more consecutive cells in that direction.
- Drop at least one stone on each visited cell, preserving bottom-to-top order, and finish with none carried. You may land on occupied cells and cover their tops. No turning, off-board step or crossing an unvisited gap is allowed. No standing stones or special pieces exist.
- Example: carry top group bottom B,top W from A1. Drop B on B1 and W on C1; those cells’ new tops are B and W. Dropping W first would reverse the lifted order and is illegal. Reserve placement cannot cover an occupied cell.
- Check roads after each turn. If both sides have roads, the mover wins. If no road and the board becomes full or either reserve becomes empty, count controlled cells: more wins, equal draws. Otherwise stop at 40 turns as a draw. Record stack contents, not only tops.
Stack-top roads — player materials
| Cell | Bottom → top |
|---|---|
| A1 | |
| B1 | |
| C1 | |
| A2 | |
| B2 | |
| C2 | |
| A3 | |
| B3 | |
| C3 |
| Turn | Place / carry group | Drops in order | Visible road? |
|---|---|---|---|
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
Continue the ledger on scrap paper, up to40 turns.
Host check — keep separate
Carried B below W drops B before W; simultaneous roads favor the mover.
Examples are stipulated model cases, not measured experimental or learning outcomes.
Related activities
Activity library · Hex edge connection: rules and printable materials