WS2812b and arduino uno fade 20 leds at the same time not the whole strip

i have everything hooked up correctly between the data pin to arduino pin 6 with 470ohm resistor external source of power with 1000uf 16v for 5m 300 led ws2812b strip. everything works can do all ytpes of examples with fastled and neo pixel but is it possible with the one data pin to input 6 on arduino to fade 20 leds on at the same time and stay on then a half a second later like delay(500); or something like that then led 20 threw 40 fade on at the same time and so on i think it would be a long code but can someone just get me started or is it even possible

is it possible with the one data pin to input 6 on arduino to fade 20 leds on at the same time and stay on then a half a second later

You can do anything you can think of that is not a logic contradiction.

It is simply a matter of changing only those LEDs in the range you are interested in. You have to write the data to the whole strip ( the show method ), but only the LEDs you change change.

thats whats im going for can someone point me in the right direction with the ws2812b. i know i want to do it with 1 data pin, id like 20 leds to fade on at the same time just 1 color lets say white or warm white doesnt matter what matters is, id like the first 20 leds to fade on at the same time half a second later something like delay(500) leds 20 threw 40 fade on at the same time all the while the first leds are still 500 milliseonds later 40 threw 60 led fade one untill all 280 leds are lit then stay lit for say 2-3 min then fade out step by step basically like stairs 20 leds each step 20 x 14 is 280 leds i tried many thing like

for int i=0; i<NUM_LED; i++ i tried for int i=0; i<20; i++

i tried for int j=0; j<(250,250,250); j++ or for int j=0; j<pixel.strip; j++

not sure if color would go there or pixel.strip or something or something like this

then i keep going a half asecond or less leds like int i=20; i<40; i++ and so on ive tried fastled library alterations, neo picel library alterations i get close but not what i want it should be so simple no colors not the whole strip at once just how i explained if someone can point me in right direction or at least start a little of the code ill do the rest ive looked for almost a year cant figuare out and change the strip colors can turn individual leds on one by one in sequeance but not 20 at the same time and not fading furthest i got is where 20 would turn on and then the next 20 would turn on but woludnt fade on im not pivking with the fade either it could be a fast fast but idk hopefully please and thank you to who ever has a little time to help just a little point in right direction or just start just a little of code then i can figuare out from there’
thank you.

Do you know what makes it east to understand what you want?
It is putting your request in sentences. That involves capital, letters, commas when appropriate and full stops. This breaks down what you want to do, so that it can be understood by someone who doesn’t already know what you want to do.

As it is I run out of breath after the first paragraph. Paragraphs are supposed to be shorter than sentences.

But to show willing what I can gather you want to do is something like this:-

for(int j = 0; j< stepsInFade; j++){
      for( int i=0; i<20; i++){
     // set colour for first 20 LEDs
    // procedure to show the results
   // reduce the brightness of the colour by subtracting the fade value for each colour element

delay(500); // I do not recommend ever using a delay here but it is simpler than implementing a state machine
for(int i = 40; i< 80; i++){
 // do stuff for another section of the code.

i get close but not what i want

So post the whole of your close attempt, in code tags ( the </> icon in the top left ) and say what it does and what you want it to do, in sentences. Then we can see where you are going wrong.

I apologize in advance, i was mad I apologize for grammar, misspelling, and incorrect punctuation. It wasn't meant to be read as wrote, it was meant to be read at your own speed, and your own pace on your own time.
Also I was a little mad not at you or anyone just in general. From trying to fade 20 leds of a 5 meter 300 led ws2812B, wait a half a secong then leds on ws2812b 20-40 leds light up while the first stay lite. And so on

Arduino Forum, I posted some code that uses segments to address the LEDS in groups. Perhaps that may work for you. Post#7

i tried for int i=0; i<20; i++

If you change that to:-

 for(int i=0; i<20; i++) {
// do stuff; // or what ever you are using

that will only work on a section of the LEDs from number 0 to number 19.

I repeat. “So post the whole of your close attempt”