From the same author Self-promotion
Rekha: an Eulerian path, drawn with your finger
Every dot, one stroke. A free line-drawing puzzle for iPhone, where each drawing is a graph to cover in a single gesture.
Rekha is developed by the author of OrigoTech. About the author
Screenshots
How it works
You must connect every dot in a single gesture. You may pass through a dot as many times as needed, but each link can only be traced once.
Version 1.0.1 at a glance
- Drawings
- 500 in total, all guaranteed solvable
- Modes
- 5: Easy, Medium, Hard, Expert and Hell, each with its own music and palette
- Daily challenge
- One drawing a day, the same for everyone
- Hint
- Shows the next correct stroke
- No
- Timer, account or lives to lose
- Offline
- Yes, the game works without a connection
- Languages
- French, English, Spanish
- Price
- Free. Contains ads: optional videos, only to get a hint
- Device
- iPhone, iOS 17 or later
- Age
- 4+
- Category
- Puzzle
Source: App Store, verified
Why it is an Eulerian path
Every Rekha drawing is a graph: the dots are vertices, the links are edges, and tracing the whole thing in one gesture without reusing a link means finding an Eulerian path.
Euler's theorem, set out around the Seven Bridges of Königsberg and fully proved by Carl Hierholzer in 1873, says a connected graph has such a path if and only if zero or two of its vertices have an odd degree (the degree being the number of links touching a vertex).
With two odd vertices, the stroke must start at one and end at the other; with none, it can start anywhere and comes back to where it began.
The game's icon, a variant of the “house” you draw without lifting your pen, is the textbook example: its two bottom corners have degree 3, so that is where the stroke starts and ends.
Source: Wikipedia, “Eulerian path”, verified
Self-promotion: this page presents a game by the site's author. It adds no third-party script, cookie or tracker, and the App Store link carries no tracking parameter.