Draw the Lines: teacher guide
Civics, US Government, or any math class that touches ratios and area. Grades 9–12. One class period.
What students will be able to do
- Explain why two legal district maps of the same voters can produce different winners.
- Define packing and cracking and perform each on a map.
- Read an efficiency gap and explain what a "wasted vote" is.
- Argue, with evidence from their own maps, whether compactness rules are enough to prevent gerrymandering.
- Describe one trade-off a real mapmaker faces (communities of interest, geography, incumbents).
Before class
Students need nothing but the link. Progress saves on their device. Play through Level 4 yourself (about 8 minutes) so you know the moment where a student realizes they can make the 40% party win. That moment is the lesson; everything else is scaffolding for it.
A 45-minute plan
| Time | What happens |
|---|---|
| 0–5 | Hook. Show a real district on the projector (Illinois 4th "earmuffs", Maryland 3rd, or North Carolina 12th pre-2016). Ask: why would anyone draw this? Take guesses; don't answer. |
| 5–20 | Play Levels 1–4 individually or in pairs. Circulate. When a student finishes Level 4, ask them to explain to a neighbor how they did it, before the game does. |
| 20–27 | Pause and name it. Students give you the words: packing and cracking. Put the efficiency gap on the board with one of their maps: count wasted votes for each side. |
| 27–40 | Play Levels 5–9. Faster students reach the finale: every district maximally compact, minority still wins. Ask them to screenshot it. |
| 40–45 | Debrief with two or three of the questions below. |
Discussion questions
- In Level 1 your map was legal. Was it fair? Who decides what "fair" means?
- You worked for Purple in Level 3 and Orange in Level 4. Did either feel like cheating? Why?
- Level 9 had the strictest shape rule possible and Orange still won a majority. If shapes don't stop gerrymandering, what could?
- In Level 6, keeping Riverside together was a constraint. Name a real community near us that would want to stay in one district. Could keeping it together ever be used as an excuse to gerrymander?
- In Level 8 the Senator drew her own district. Who draws the districts in our state? (Look it up: a legislature, an independent commission, or a court.)
- The efficiency gap flags maps above about 7%. Is a number like that a good legal test? What's a weakness of it?
Misconceptions to listen for
- "Weird shapes mean gerrymandering; normal shapes mean it's fair." Level 9 is the counterexample. Shape is a clue, not proof.
- "The party with more voters always wins more seats." Levels 4, 7 and 9 break this directly.
- "Gerrymandering is a one-party problem." Students play both sides on purpose. Both parties do it where they control the pen.
- "Equal population makes it fair." Every level enforces equal population. It is necessary but nowhere near sufficient.
Extensions
- Students design their own level on graph paper: a grid, a goal, and a solution. Check it with a partner.
- Research: Rucho v. Common Cause (2019). What did the Supreme Court decide about partisan gerrymandering and federal courts? Where do those cases go now?
- Math tie-in: compute Polsby-Popper by hand for two of your districts. Compactness = 4π × area ÷ perimeter². Why does a circle score 1.0?
- Compare the efficiency gap to a simpler test: seats-minus-votes. When do they disagree?
About the numbers in the game
Each cell is one voter and districts must have exactly equal population, which is stricter than real law (real districts allow small deviations). Compactness uses the Polsby-Popper score on grid cells. The efficiency gap follows Stephanopoulos and McGhee (2015): wasted votes are all votes for a losing candidate plus winner votes beyond a bare majority, and the gap is the difference in wasted votes divided by total votes. The 7% threshold is the one they proposed for legislative maps; courts have not adopted a fixed number.