Knotilus

Knotilus is a daily number puzzle built around Fibonacci-like sequences, where each number is the sum of the two before it. The daily challenge gives you a pool of four to ten such sequences and asks you to find the three that meet at a single shared number, the "knot," while all their other numbers stay unique. You solve it with addition, pattern recognition, and deduction rather than luck.

What is Knotilus?

At its core, Knotilus is about additive sequences. A Fibonacci-like sequence starts from two numbers and continues by adding the last two together, so the shape of each sequence is set by where it begins. Each day the puzzle presents a pool of these sequences, somewhere between four and ten of them, and your job is to reason out which three form the solution set. The solution is the group of three sequences that overlap at exactly one common number, the value the puzzle calls the knot, while every other number across those three sequences appears only once.

What sets Knotilus apart from most daily puzzles is that it is not a guessing game dressed up with math. You are not trying to land on a hidden answer through feedback and elimination the way you would in a word game. Instead you study real numeric structure: comparing where sequences cross, checking which shared values are true knots and which are coincidences, and confirming that the three you pick do not share any number other than the single knot. The addition is simple, but the deduction about how the sequences intersect is where the puzzle lives.

Knotilus has a few options to fit how you want to play. You can set a difficulty level, which changes how many numbers are available to build sequences from, and you can turn a mode with helpful visual indicators on or off. The creator notes that the solution stays the same no matter which difficulty you choose, so the settings change how much help you get rather than the answer. Hints are also available if you get stuck, and the puzzle can compare your results, such as your time and how many hints you used, anonymously against other players.

The game was shared publicly on Hacker News as a "Show HN: Knotilus" post on January 3, 2025 by its creator, who posts under the username mdduar and describes themselves as a hobbyist web developer. The creator's real name is not given. It runs in the browser at knotil.us and is free to play, with no downloads or installs, which fits the small, self published feel common to daily math puzzles that circulate through communities like Hacker News.

In practice a session is short and focused. You look at the day's pool, work through the sequences by adding forward, and hunt for the one shared number that ties exactly three of them together. Because a fresh puzzle is generated each day, the difficulty comes from how tangled the overlaps are rather than from the arithmetic. It rewards patience and careful checking: a value that looks like the knot can turn out to be shared by the wrong count of sequences, or two candidate sequences can share a second number and quietly disqualify themselves.

How to play Knotilus

1. Open Knotilus at knotil.us in your browser.
2. Read the day's pool of Fibonacci-like sequences, noting that each number is the sum of the two before it.
3. Extend each sequence by addition so you can compare the numbers they contain.
4. Look for numbers that appear in more than one sequence, since a shared value is a candidate knot.
5. Find the three sequences that meet at exactly one shared number, the knot, and confirm none of their other numbers repeat across the trio.
6. Select those three sequences as your solution for the day, using a hint if you get stuck.

Tips and strategy

• Work each sequence forward so you have its numbers written out before comparing them. The addition is easy but easy to slip on.
• Focus on shared numbers first. A knot must be common to your three chosen sequences, so scanning for repeated values narrows the field fast.
• Remember the target is exactly three sequences at the knot, not two and not four, so count how many sequences contain each candidate value.
• Watch the disqualifier too. If two of your candidate sequences share a second number, they cannot both be in the solution.
• Since sequences are defined by their starting pair, small differences at the start lead to large differences later, so compare early terms carefully.
• If you are new to the puzzle, turn on the mode with visual indicators or lower the difficulty. The solution stays the same, so you lose nothing by using the help while you learn.
• Take your time. The puzzle is about deduction, not speed, and a careful pass usually beats trial and error.

Good to know

Category

Math and logic

Resets

Daily, at midnight in your timezone

Cost

Free

Launched

January 2025 (shared on Hacker News)

Creator

mdduar (Hacker News username)

Platform

Browser (knotil.us)

Concept

Fibonacci-like sequences with a shared "knot" number

Pool size

Four to ten sequences per day

Goal

Identify the three sequences sharing exactly one number

Knotilus FAQ

Is Knotilus free?

Yes. The puzzle is free to play in the browser at knotil.us with no downloads or installs.

How do you play Knotilus?

Each day you get a pool of four to ten Fibonacci-like sequences, where every number is the sum of the two before it. You use addition and logic to find the three sequences that share exactly one common number, the knot, while all their other numbers stay unique.

When does Knotilus reset?

A new puzzle is made available every day at midnight based on your timezone.

Does Knotilus have difficulty settings or hints?

Yes. You can set a difficulty level, which changes how many numbers are available to build sequences from, and turn a mode with helpful visual indicators on or off. Hints are available too, and the solution stays the same regardless of the settings you choose.

Is Knotilus like Wordle?

Not really. Both are daily puzzles, but Knotilus is a number and logic puzzle built on Fibonacci-like sequences rather than guessing a hidden word through letter feedback. You deduce which three sequences meet at a single shared number.

Who made Knotilus?

It was shared on Hacker News as a "Show HN" post in January 2025 by its creator, who posts under the username mdduar and describes themselves as a hobbyist web developer. Their real name is not given.