Growing up, I watched my mom do mental math at the market without missing a beat — three bundles of rau muống at 8.000đ each, two con cá lóc at 45.000đ, change for a 100k note — all in her head, all in seconds. I always thought that was a skill worth preserving.
Market Math started as a weekend Flutter experiment: what if I built a game around that exact experience? You're at the chợ, the vendor is waiting, and you have to add up your basket before the timer runs out. Simple premise, surprisingly hard to put down.
The interesting design problems showed up fast. Vietnamese prices work in thousands — nobody says "45,000 đồng," they say "45 nghìn" — so the number pad had to reflect that (type "45", the game reads 45.000đ). The catalog needed real items at real prices: rau cải, thịt ba chỉ, dưa hấu, with regional name differences between Miền Bắc and Miền Nam baked in. I ended up with 83 market items and a question generator that randomizes prices with believable variance.
When I added English/US support, the whole pricing layer had to split. American players get a dollar-based catalog — 87 items, whole-dollar prices, no regional variants — but the underlying math engine is the same.
The vendor personalities were the most fun to build. Each of the six market themes has a named character: Chị Bảy from Bến Thành, Bác Hùng from Đồng Xuân, and so on. They greet you before the game and react to your score afterward — a different pool of praise or gentle ribbing depending on how well you did.
The app is live on iOS and Android. It's a small game, but it's the most Vietnamese thing I've ever shipped.
