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LYNXware CAT review

The CAT by LYNXware is an incredible input device with a great potential. That said, you'll need some time to get accustomed to the custom software, the terminology, 22 thumb keys – and mouse switches!
Published February 23, 2024
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The LYNXware CAT is the creation of Stanislaw Kirpicnikow aka Ape_Devil from Germany. This modular device is available both as a prebuilt product and as a well-documented open-source kit sporting mouse switches.

TLDR; Combining modularity with excellent build quality, the LYNXware CAT has great potential. While it's definitely not for the faint-hearted (no legends, custom software, Engram layout as default), 11 thumb keys per half within a comfortable distance may be a game-changer for many. I personally am ready to put more time into experimenting with the layout to be able to completely replace a keyboard and mouse with a single device, however, lighter switches are needed for typing, and the software part has to be improved too.

I'm calling the CAT a keyboard with some caution because despite apparently akin to a 3D printed split keyboard, it uses mouse switches. Yes, mouse switches! A double-edged sword in my experience, with both benefits and challenges. And speaking of mice, the CAT may act just like that, a decent vertical mouse!


I first wrote about the CAT project in 2021, and then last month, after seeing the incredible improvement, so was very happy when Stanislaw offered to send me this unit. As always, receiving a free review unit may introduce both positive and negative bias. Read everything below accordingly.

Contents & First impressions

Very carefully packed, looks awesome despite being 3D printed.



If I didn't know one half was a mouse I'd think it was a neatly sculpted split. Had to look up the default layout though. Engram?! Pure evil. :D


Contents: Two halves, two cables, three optional palm extensions per half, leaflet. Everything carefully packed.


Given the CAT is a modular device, you can choose from a bunch of variants for the finger and thumb pieces: with joystick, roller encoder, just keys, etc. Or with mouse, gyroscope in the halves.


My primary goal was to test if it's possible to ditch a dedicated mouse while using the CAT for blogging/coding/image processing, so I opted for the all-key version with a built-in mouse in the right half.


A roller encoder would have been nice too, but typing in multiple languages, I decided to wait for a thumb cluster with encoder rather than sacrifice three keys on top.


Forget about plug-and-play in the sense using the CAT right out of the box – unless you happen to touch type on Engram layout. Forget about QMK or Vial too, let's dive in the LYNXapp, which is intuitive, but you still have to get used to it since there are some significant differences when compared to Via/Vial.

Fortunately, there is a step-by-step video tutorial on what to do, I'd suggest to start with this:

To sum up, you have to download the LYNXapp software (open-source) and familiarize yourself with a new terminology which may add to the initial confusion: Major/minor, main/sub are the layer names here, accessible with dedicated keys. These work as tap/hold (but no other keys at the time of writing this if I'm correct)!

Layout and build quality

The all-key CAT has a 20-key finger area per half. This is basically the familiar split 6x3 arrangement with some twists: one key less in the outer pinky and the inner index columns, plus an extra row for your longer fingers.

The arrangement is "ergolinear"-ish, which means it follows a grid with exactly 1U pinky stagger. The only exception is the inner index column, which has a 0.5U offset.


The build quality is really good, with clever friction fit solutions everywhere – no screws at all. E.g. you can simply open the bottom of the housing and by pressing the finger area outwards you can remove the modules for inspection or replacement.

Mouse switches

So instead of the familiar MX or Choc switches you have to deal with tiny mouse switches here.


This results in some major differences when compared to keyboards with common keyswitches, affecting typing both in negative and positive ways:

  • heavier weight
  • much more compact layout (both finger area and thumb cluster)

Layout and pitch

Thanks to the mouse keys, the spacing is dramatically reduced. Instead of the 19x19 mm classic (or 18x17 Choc, 17x17 CFX) spacing, it's about 8 mm on the CAT. In a reduced range of movement of only 3.6 cm you can reach every single key of a 4-key column.


Of course this requires some practice, since with the compact layout comes a new challenge: no sloppy typing anymore, sorry folks. This is a precision device requiring accurate handling, so expect an appropriate learning curve.

Thumb cluster

With classic splits, 3-key thumb clusters became the standard. Any more keys and they interfere with something or result in stretches/strain.

On the CAT you can have 11 thumb keys per half, while keeping the almost same range of movement compared to a 3-key thumb arc of an MX-spaced split.


After a few minutes of practice you can feel your exact location due to the different types of caps. I'm not sure if the dimensions of the switches would allow a more radial arrangement of the thumb keys, but it would bet the icing on the cake.

Switch weight

My unit came with these switches, 80±15gf. That means 65-95gf in theory! According to my raw measurements, the inconsistency is even more extreme in practice: 40-80gf. What's even worse? This is not across switches but in case of a single switch: the very same switch may trigger at 40gf, then the next time at 80gf. It's pretty impossible to prepare for this while typing.


In my experience, this pretty extreme inconsistency in switch weight mainly affects rolls. Despite the familiar split layout, my keymap perfectly recreated, I still wasn't able to churn out rolls as usual.

Practicing in my case meant I had to do some exercise to gain enough strength, but even that does not solve the problem of inconsistency.

The mouse switches feel even heavier because of the tiny caps and the tenting. Using a conventional flat MX board, a thick double-shot keycap and also the weight of your resting fingers can help the downward movement, reducing the required force to operate the switch. With tiny caps and a relatively extreme tenting of the CAT, both components are missing from the equation here.

I'm really not into mouse switches but made a quick research, and one of the hailed models on the lighter end of the spectrum is the TTC Gold 80M with 60±15 gF. While this is still heavier than my favorite linears, it might be worth a test.


The CAT comes with basically three types of 3D printed keycaps: convex, concave, and concave with a tiny homing bump – as you can see, all of these come in a circular shape.


Pic: Backside of keycaps

Backside of keycaps

Thanks to the tiny size and the basic structure (no stem), they look very easy to reproduce and replace. This may come in handy if you'd like to make your own caps.


Having a dedicated software sitting on your host computer has both benefits and drawbacks. I'd say the firmware/software functionality is the weakest part of the project, which has to be improved to get out the most of the CAT.

First of all, the two halves are two devices, you need two cables, occupying two USB connectors. (They sense each other's mod keys though.)

Secondly: I had to replug them each time coming back to my PC after it went into sleep mode. Stanislaw is aware of this, and fixing the issue is top priority.


At this time I could only achieve double-function mod-tap behavior with the baked in layer keys (major/minor, main/sub). Given the large number of thumb keys you have plenty of room for keymap optimization, but I'd say recreating some common QMK functionality should be the next step on the todo list.

Benefits? You can easily swap layouts by copying files.

Other than that, the CAT automatically adapts to the system language. E.g. if you change your system language, it may load the appropriate keymap.

This is probably irrelevant for people typing exclusively in English, but may come in handy for Europeans with all the funny accented characters – when set up properly of course. :D


The interface is intuitive, I like it in general. You assign functions the good old point-and-click way, however, the list of keycodes, especially the arrangement, could be closer to the standard Via/Vial solution – i.e. an ANSI/ISO keyboard.


Despite the familiar layout and keymap, my very first attempt resulted in a devastating 20 wpm. :D After half an hour of practice I could consistently do 40 wpm, let's say I was on par with the overall average typing speed of humanity (42 wpm I guess). My first 60 wpm came 110 minutes into practicing.



My improvement in the first two consecutive days was impressive, making it from 20 to 60 wpm with only 2-3 hours of practice, spending half of the time with tweaking my layout and taking notes. However, after one day skipped, I arrived at a very discouraging plateau. That's what you can see in the graph. That said, I'll try to keep practicing.

You can definitely make gradual progress, which is encouraging, but it's quite a workout after all the light switches. Most of the typing issues stem from the relatively heavy and inconsistent switches: rolls often don't work as expected, with keypresses either not registering or bursting out multiple letters.

Mouse function

How fast and efficient you can tame your CAT mouse while typing – this is the keyword here! – may depend, at least in my experience, on the underlying surface: a leather deskmat worked the best, followed by other deskmats I have at hand. Using the CAT on the bare desk surface, it was almost uncontrollable – however, with the sensitivity turned to the max because of the two-monitor setup.

The problem is, you have to balance between optimizing for keyboard or mouse functions: As a mouse, it had to be easy to move and slide. As a keyboard, it should be solid and stable.

Lighter switches or more weight in the mouse half would definitely help, because now pressing some keys may move the mouse.

I ended up disabling the mouse function in general and enabling it only on a dedicated layer. This way I can turn it on/off by pressing a thumb key, which seem to work for me.

Palm extensions

The CAT came with 3-3 palm extensions for both halves, in different sizes. I tried all of them but ended up using the device without any of those mounted. I use my keyboards with my forearm resting on the arm rest of my chair too, so didn't feel any more support was necessary.


What I like the best?

  • It's strange, but I like the thumb cluster. 22 keys, 11 per half, but you can easily reach all of them.
  • The layer indicator LEDs on the thumb cluster are cool too. Very well placed, clearly visible while in use. Useful in the familiarization phase.
  • Mouse switches allowing a very compact arrangement of the keys: about 8 mm vertical spacing! Less finger movement. I really think the concept has great potential, just the perfect switch type has to be found – or designed.

What I liked less?

  • Replugging both halves every time my PC is waken up
  • too heavy switches for typing, at least for my taste and fingers
  • the deviance of LYNXapp: order of keycodes/functions, terminology, etc.


I cannot stress it enough that I believe in the CAT: it's a great project but not a perfect product yet. In its current form it's a bit bulky as a mouse, and the mouse half is a bit unstable as a keyboard. I guess it's hard to finetune this and to come up with a sweet spot, which may depend on personal preference.

That said, this is only a problem if you'd like to use the device both as a keyboard and a mouse, and at the same time. ;)

Let's hope the software quickly catches up with the hardware, and other than that, I'm sure different switches would solve many of my problems too. Since the CAT is modular and open-source, you have plenty of options to tailor it to your needs, and I may order some replacement switches too.


And in case you are interested, here are the accessories in the photos, in order of appearance:

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Published on Fri 23rd Feb 2024. Featured in KBD #156.


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