I've made a Microwriter kbd so I can keep one hand on my mouse and one hand on it.
I'm still quite slow but getting quicker the more I use it 
Programmed it up on a micro-controller using MicroBlocks
(not all code shown)
This is beyond cool! Did you design the case yourself, too?
This is cool, but how would one use said keyboard?
Ignore this. It was wrong.
I believe that there are keys on the mouse. Presumably there are enough keys that one can do the rest of the typing with their other hand. On a QWERTY keyboard the keys on the mouse might be:
YUIOPHJKLNM,./ and maybe ' and ;. Shift could be used on the other side to achieve capitals and other symbols.
Edit: just realized this is a lefthanded mouse. Revised keys:
QWERTYASDFGZXCVB. Maybe shift would be on there as well for typing letters with the pinky finger while holding shift (i.e. P, :, ", and ?).
Basically, you can type with just one hand using the small number of keys (5) on the hand shaped keyboard. Combinations of keys pressed at the same time provide different characters. More details are in the document linked to in the first post. Presumably this is left-handed so that the right hand can be on a mouse (because who wants a keyboard without a mouse). But don't quote me on that.
I use TinkerCAD too!
Check out the manual
oh okay cool
I was asking how one would operate your mouse, not how it functionally worked
Is not a mouse its a keyboard
I meant keyboard, apologies, I'm a bit tired today
It's a keyboard not a mouse. Checkout the linked manual
I just did and was about to edit my post 
.
Edit: Edited!
Our posts passed in the ether
This is cool; it's like the workstation Doug Engelbart designed when he invented the mouse, way back when. (Except that iirc his left hand keyboard wasn't hand-shaped but instead was in front of your hand like a piano keyboard.)
This is really cool. 
Exactly
How'd you get the Microblocks to act like a keyboard?
You need to use a micro-controller that can act as an HID device e.g. RaspberryPi Pico
And then load in the Keyboard and Mouse library in MicroBlocks
tab, shift-tab, arrow keys, and enter keys my beloveds
Indeed. Don't forget ctrl-tab, ctrl-shift-tab, alt-tab, alt-shift-tab, ctrl-T, ctrl-shift-T, fn-f11, windows-shift-s, windows-tab, etcetera. But a) a mouse is still nice for other things (you need to click on the keyboard icon to enter keyboard mode in Snap!) and b) I'm don't think that this keyboard has shift, tab, ctrl, fn or any other special keys.