Only the streets count
The tiles are about 87 metres across around Perth and Busselton, and only the ones with a street or path you can walk on count towards your 100%, so you're never stuck needing to swim across a lake. Patches with no path, like bush or wetland, clear all at once when you walk a tile next to them.
Walking only
Bikes and cars don't count, so no clearing your suburb from the car window. Walking and jogging do as long as you're under about 12 km/h, and if the phone's motion chip reckons you're cycling or driving it doesn't count however slow you're going.
Always on
If you give Walkies "Always" location access, it notices when you head out on foot and records the walk by itself, then ends it once you've stopped for ten minutes. You can switch it off in Settings and just press Start walk when you go.
Tiles go misty
If you haven't walked through a tile for two months it goes a bit misty, so you can see which bits you haven't been back to in a while. It doesn't take anything off your % or your shells, and walking through it again clears it.
The suburb next door
When you zoom out, the suburbs around yours have a little + button so you can add them too. Every place uses the same grid so the tiles line up across the border, and any walks you've already done there count straight away.
Teams
You can start a team with up to eight people and send them an invite link. Right now a team is just who's in it, with everyone's name and colour, and your clouds and secrets stay your own.
Where the idea came from
My mate James, who's the CTO at Convex, told me about a walking app he'd been working on where you try and walk every single street in your city. I never actually got to see it, and he said he was going to open source it, but I got too impatient and decided I could build my own.