The split between a one-minute walkthrough and a two-minute lesson on Suppose is the right shape, but the first case should only force one success: name who was alone with the victim. Keep Suppose as the recovery that appears the first time someone stalls on a contradiction, not as required reading before Monday. If Gentle still needs both lessons up front, the default path is already longer than the puzzle. One-word labels on the hint buttons, saying what they reveal rather than only the cost, will do more than another paragraph of rules.
Thanks, this was really useful - I've addressed your points in version 0.11.0 which is up now. The one-minute walkthrough coaches two squares and then just asks for the name of who was alone with the victim and the suppose lesson is gone from the opening screen. Suppose now just turns up once, when someone stalls on a case that needs it the first time. The hint buttons say what they show: “Where to look”, Next step”, “Answer”. If you happen to play a few more days, I’d love to hear whether the hints are pitched right on the Tricky and Fiendish cases.