Tricky Circles by Dmitry Chalovskiy is one of such games.

After seeing the icon, I feared that it was just another clone of the boring Dots, but thankfully it's something completely different.

The tutorial isn't great in explaining what you have to do, so it took me a couple of attempts to get it.

Your task is to draw a continuous line that touches all the circles. The catch is that going from one circle to the next you'll move by the number of positions shown inside the circle.

So in the example above, you start from the left circle. It is a 1, so you move right by one position. That's a 2, so you then move right by two positions and land on the rightmost 1. Now you move left by one position and you're done. Note that it's legal to go back in the direction where you came from.

Also, you must draw the path with a single gesture. If you lift your finger and haven't solved the puzzle, you must restart from the beginning.

You can move only horizontally and vertically, not diagonally. Also, there are occasional black circles, which serve no purpose. I don't understand why they are there: they could simply be replaced by an empty space.

Mathematically, these puzzles are equivalent to searching for a Hamiltonian path in a directed graph.

I quickly solved the first few puzzles, and then got stuck on puzzle 8.

Interestingly, taking a sheet of paper and drawing the equivalent graph helped me see things more clearly. So we can probably say that the visualization of the puzzles is a way to obfuscate the structure of the graph they are derived from.

**SPOILER WARNING:**skip the next paragraph if you want to solve the puzzle by yourself.

The key is that the two 2 pointed to by the arrows can only be reached by the 1. Since there's no other way to reach them, one of them must be the beginning of the path. It's easy from there.

In another puzzle I found a circle that didn't lead anywhere, so it had to be the end of the path.

In general, the solving process reminds me of Disctrail, but here you have less freedom.

There are 21 free puzzles, which must be completed in sequence. With an in-app purchase you can buy 21 more puzzles, which again must be completed in sequence.

These puzzles are harder than they might seem. Definitely give this game a try.

### Summary

Nontrivialness | ★★★★☆ |

Logical Reasoning | ★★★☆☆ |

User Interface | ★★★☆☆ |

Presentation | ★★★☆☆ |

Loading Time | ★★★★★ |

Saves Partial Progress | ✘ |

Status Bar | ✘ |

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