Terrax is a fog of war map for real life. The whole world starts out covered in fog, and it only clears where you actually go, on foot, by bike, by car or by train. So it's part walking game, part step counter, and slowly a map of everywhere you've been.

The first week is the fun part. You walk to get coffee and a small hole opens in the fog. You take a different street home just to watch it clear. A few days later your neighborhood has a shape, and you start noticing the gaps: the block behind the grocery store, the park you've driven past for years and never walked into. That's pretty much the whole idea.

How it works
• GPS clears the map in squares about 80 feet (25 m) wide, and whatever you uncover stays uncovered.
• Leave your phone in your pocket with the screen off. Terrax keeps tracking in the background.
• Walking, running, biking, driving and trains all count. Planes don't. No clearing half the country from 35,000 feet.
• No signal on the trail? Exploration keeps recording, and the map background loads again once you're back in range.
• A home screen widget shows today's steps and how much you've explored.

The step counter
It's a real pedometer that uses your phone's step sensor: today's steps, a daily goal you pick yourself, and a streak to keep alive. So the dog walk, the commute and the Saturday hike count twice, once for your steps and once for your walking map.

Countries visited
Terrax spots the countries you pass through on its own and adds the flag. No checklist to fill in. You also see how much of the world you've uncovered, in percent and in area, and which continents you've been to. Over time your fog of war map turns into a travel map, a bit like a scratch-off map that fills itself in.

Long drives count too. After a road trip, the route you drove shows up as a trail cut through the fog, along with the small towns where you stopped to stretch your legs. Terrax won't plan the trip for you. It just remembers where you actually went.

Friends are optional, but it's more fun with a couple. You add each other with a friend code, compare fog of war maps, and see each other on a friends map at the precision you choose (exact, about half a mile or about 6 miles). Ghost mode hides you whenever you want. There's a friends leaderboard, a worldwide one, and a year-in-review style poster you can share.

What's free, what isn't
Free, with no ads: full tracking, the step counter, countries visited, 2 friends, 6 months of history and the shareable poster (with a watermark). You can also export your tracks as GPX files anytime.
Terrax+ is an optional monthly or yearly subscription. It adds a 3D globe, extra fog styles (starry night, pink aurora, deep jungle and a few more), satellite and terrain maps, unlimited friends and history, advanced stats, a personal heatmap, the poster without a watermark, and importing your old trips from Google Maps Timeline or GPX files, so places you visited before Terrax show up too. Cancel anytime in Google Play.

Your location stays yours. Your data is never sold. Nobody sees you on the map unless you've accepted them as a friend and turned sharing on. Your map is backed up with your account, so a new phone doesn't mean starting over, and you can delete your account and data at any time, in the app or on the web.

Terrax is made by Victor, an indie developer in France. There's a Report a bug button in the app, plus a roadmap where you can suggest ideas and vote on them. He reads all of it.

Go for a walk and see what's under there.

One heads-up: GPS running in the background does use some battery.