• ✓Idea: which way a line leans is information — ╱ is not ╲
• ✓This is what has to come before telling b from d
• ✓Each mark has its own shape as well as its own colour
• ✓Four, five or six marks — a step at a time
• ✓Turn it into a printable sheetplanned

✓ = done · ☐ = planned. Every game is built one step at a time like this.