Trailmarks iOS - Real World Travel Quiz & Trivia Adventure

Trailmarks is a travel trivia game built on the real world. You answer true-or-false questions about the city you're in, then spend the rewards on a ticket out, limited by what the departure board offers and what you can afford. Your score is the kilometers behind you. The routes are real: flights that exist, trains where there are tracks, boats across oceans. 1000+ cities. iPhone only, $4.99 once, no ads, no account, plays fully offline.

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I've wanted to make this game for decades. The dream was a trivia game where you don't compete on correct ratios or time, but where the challenge makes up a journey, or a campaign, so to speak. In Trailmarks, the score you get is always the kilometers you travelled, with mostly real world flight routes, railroads and buses. The problem was that to feel deep, it needed thousands and thousands of questions, and that was just never possible before LLMs. Before Claude I experimented with fill in the blank type questions from Wikipedia and pre-LLM generated text, which didn't scale very well. The big question, though, is obviously how to avoid hallucinations. For this corpus of true/false questions, I based it on four pillars: * Let the LLM create the headline topics (much more likely to have content) * Have completely different models try each question, remove every question where they don't converge. The risk is convergent hallucinations, but that turned out to be a much lesser problem than expected. The models also diverged so much that over 50% of the original "facts" were removed. * Take samples to manually check correct rate (In 2,000 we found 0 errors, giving us an upper boundary of 0.2% error rate at 95%) * Provide the source material (to a lesser degree in this release) The downside is that the occasional particularly fun fact might be lost because not every LLM knew it. Also, to my surprise, we lost a lot more questions than I expected when cleaning it up for Apple's Age rating - at the outset I thought LLMs would generally avoid sex and drugs, but apparently not. So around 1000 questions about cocktails, local wines and red light districts also had to go.