Design

Goals

Dusk was designed with these goals in mind:

Roll over Alternation
Low scissors
Low 2u SFS (including some fast X__Y)
Low SFS
Low SFB
Low finger speed
Fair workload for each finger

Coming from Canary, I'd like to focus on keeping its low scissors and 2u SFS, while optimizing for SFS and keeping an eye on SFB.

Dusk was designed with info obtained with corpus made out of MonkeyType and Typeracer quotes (duplicates removed), with some SHAI corpus sprinkled in.

Vowel Block

I decided to go with the popular vowel block

~ ~ ~ ~ ~  ~ ~ O U .
~ ~ ~ ~ ~  ~ ~ A E I
~ ~ ~ ~ ~  ~ ~ ~ / ,
        ~

as EO is the primary source of SFS on Canary and OU AEI vowel block is commonly agreed upon to be the most balanced vowel block choice in modern days. Having I alone on the pinky for the .I, stack.

Why vowel block? because vowels don't go well with most letters, but they go relatively well with each other.

If you type ./ or ../ often, you may want to swap .,.

Consonants

`LHM`

To avoid RL SFB, I decided to put R on a thumb key (as opposed to the RN stack as seen in Kuntum). L doesn't really go well with any other letter except for H and M, but L_M and M_L are both somewhat common, which leads to LHM stack having high 2u SFS if its on a non-index column, so LHM goes to index with M taking the inner spot, just like in Canary. If you are more bothered by LSB than 2u SFS, it would be wise to move M to the top.

~ ~ ~ ~ ~  ~ ~ O U .
~ ~ ~ ~ ~  M H A E I
~ ~ ~ ~ ~  ~ L ~ / ,
        R

`DTK`

T index commonly leads to high SFS in my experience playing around with layouts for the past few months, so I settled on DTK stack, which is a good load for the middle finger to handle.

~ ~ D ~ ~  ~ ~ O U .
~ ~ T ~ ~  M H A E I
~ ~ K ~ ~  ~ L ~ / ,
        R

`BNZ`

I like the idea of having N on the pinky because they promote inroll with S, T, C and tend to be have lower redirection and scissors especially now that R is gone (usually N pinky layouts end up with BR scissor like in Graphite and Gallium).

N doesn't interact with B much and with a low-usage key Z, BNZ goes to pinky. X wasn't chosen out of concerns for the interactions with the columns that follow below.

B ~ D ~ ~  ~ ~ O U .
N ~ T ~ ~  M H A E I
Z ~ K ~ ~  ~ L ~ / ,
        R

`FSV`

ST in-roll sounds like a good idea and S doesn't have good letters to partner, so I decided on FSV stack for the ring finger.

B F D ~ ~  ~ ~ O U .
N S T ~ ~  M H A E I
Z V K ~ ~  ~ L ~ / ,
        R

Wait a minute!

You may think, "wait a minute! but that creates NV scissor and awkward DV !". Yes, I hear you, so there is another variant dusk-vq that addresses this concern.

What's the trade-off?

Pros:

no NV scissor (involve)
no DV (advice)
no b_v skip scissor (above)
no f_v 2u SFS (favorite)

Cons:

w_v 2u SFS (however)
g_v 2.23u SFS (give)
v__g 2.23u SFS (loving)
rv and v_r may be weird for some (service and very).
6 keys to look after for left index.

`PCGWY`

Y is yet another problematic letter as it creates CY, PY, GY SFBS and W_Y is common enough that I'd like WY to be 1u apart. I decided on

B F D P ~  ~ ~ O U .
N S T C Y  M H A E I
Z V K G W  ~ L ~ / ,
        R

because:

I want NG to be a nice roll and a good G_T (-ing, -ght, get, got).
C is usually more common, so it is on the homerow.
Y is there for the ease of alting CY, PY, YP and (optionally) GY.
W is under Y because W_Y is common, in addition to YW SFB. It is not above Y because W_T, W__T, W__K, TW and WR all feel awful. I am okay with P_W or W_P 2.24u SFS as they are rare.
P takes the last good spot and creates PY and YP alts.

I don't want to alt!

If you don't want to alt/slide CY, PY, YP, GY, and WY, and get deeply annoyed with them. May I suggest that you do

B F D P ~  ~ ~ O U .
N S T C Y  M H A E I
Z V K G W  ~ L Y / ,
        R

Now you have 2 Y that you can choose to use according to the words in question.

`QJX`

J goes well with vowel inner top spot because JU accounts for most of J appearances.
X does not go well with C and P (excel, expect), so it goes to vowel inner bottom spot.
Q takes the last remaining index spot at consonants side.

B F D P Q  J ~ O U .
N S T C Y  M H A E I
Z V K G W  X L ~ / ,
        R

Quote Symbol `'`

Other layouts commonly have OA' stack on the middle finger, but after using other layouts that have this stack, I've come to dislike it. Here is why:

You' feels like 2u SFB even if it is 2u SFS. For me, ou is a roll, so my middle finger tends to not leave for ' until after u has been typed.
don't and won't feel just awful with how common they are.
Additionally, a_' is common too (that's, can't, what's).

For the aforemetioned reasons, I decided to go with

B F D P Q  J ' O U .
N S T C Y  M H A E I
Z V K G W  X L ~ / ,
        R

with the intention to alt 'm and 'll, both of which are doable for my columnar keyboard. If you do not want to do 'll alt, I think it is still preferable over OA' stack. (I do not believe 'll alt is feasible on rowstag keyboard).

It does create h_' SFS, but it is about as common as a_'.

Alternative 1

Embrace the OA' stack like the layout below shows - all the pros and cons have been explained above.

You may want to swap J~.

This results in 0.10% lower SFB and 0.29% higher SFS on MonkeyRacer corpus.

B F D P Q  J ~ O U .
N S T C Y  M H A E I
Z V K G W  X L ' / ,
        R

Alternative 2

Swap QJ'.

Keep in mind that it creates

Y' SFB (They')
W_' SFS (We')
DN' redirection (don't)
C__' SFS (can't)

It results in 0.04% lower SFB and 0.01% lower SFS on Monkeyracer corpus, but it increases redirection by 0.59% on according to Cmini, attributed to t's and n't. Additionally, both 't and t' do not feel good to me.

B F D P '  Q J O U .
N S T C Y  M H A E I
Z V K G W  X L ~ / ,
        R

Alternative 3

Put ' at both empty spots. Use the bottom ' for 'm and 'll.

B F D P Q  J ' O U .
N S T C Y  M H A E I
Z V K G W  X L ' / ,
        R

Last Spot Options

It's free real estate. I decided to put underscore _ there because I code in C++ and Rust often.

Here are some ideas:

;
Y
'
Repeat Key (creates LL outroll)

B F D P Q  J ' O U .
N S T C Y  M H A E I
Z V K G W  X L _ / ,
        R

Final Adjustment

One user of Dusk, brownfoxjumps, mentioned that he was using dusk with BZ swap. This got me thinking - as Dusk it is now, words like above, back, break, obvious, and keyboard all require whole hand movement due to (skipgram) scissors. If BZ is swapped, then the only key that would be of concern is the top ring key F, but B and F don't really interact with each other much at all - except for the word before. b_d and prob- still don't require hand movement and feel fine. I decided that swapping BZ is worth it.

Z F D P Q  J ' O U .
N S T C Y  M H A E I
B V K G W  X L _ / ,
        R

With Z up there, it now raises the question of whether it is worth it to swap XZ. Personally, I think it is worth it because 2 out of the 3 reasons that I chose Z instead of X were that XP is awkward and the f_x scissor. With these two reasons no longer applicable, I think it is worth trading the rare 2u pinky SFS (box) for taking 0.01% lower SFB and 0.05% lower SFS (SHAI corpus) off from the finger with the highest SFS and SFB, and that sweet XP inroll (expect, experience).

X F D P Q  J ' O U .
N S T C Y  M H A E I
B V K G W  Z L _ / ,
        R

What about `FV` swap?

Some of you may be wondering: why not the following layout? Doesn't it address b_f and dv while not losing out much (g_v but it is no big deal)?

Z V D P Q  J ' O U .
N S T C Y  M H A E I
B F K G W  X L _ / ,
        R

I toyed with this idea for a while and came to the conclusion that it is not worth it because of f_nd, which is quite a lot more common than dv on dusk while feeling worse than it.

Summary:

Pros

dv roll
b_f same row

Cons

f_nd skipgram redirect 2 row jump
xz forced swap or getting f_x skipgram scissor
bv/b_v 2 row jump

Dusk Keyboard Layout