Neopixels moving between rainbow colours

microbit rainbow

input.onButtonPressed(Button.A, function () {
    maxb = maxb <= 0 ? 0 : Math.max(maxb - 10,0)
})
input.onButtonPressed(Button.B, function () {
    maxb = maxb >= 255 ? 255 : Math.min(maxb + 10,255)
})

input.onLogoEvent(TouchButtonEvent.Pressed, function() {
 reverse = !reverse   
})

input.onButtonPressed(Button.AB, function () {
    speedIndex = speedIndex >= speedOptions.length - 1 ? 0 : ++speedIndex
    showValueTime = input.runningTime()
    basic.showNumber(speedIndex)
    
    
})
let stretch = 2 // Set to 1, red will wrap instantlty from left edge to right. 2 will simulate a circle. Higher will stretch out the colours
let showValueTime = 0
let displayTime = () => input.runningTime() - showValueTime
let speedOptions = [50,40,30,20,10,0]
let speedIndex = 3
let maxb = 100
let hslElementCount = 300
let ledCount = 13
let strip = neopixel.create(DigitalPin.P0, ledCount, NeoPixelMode.RGB)
let offset = 0
let gap = Math.floor(hslElementCount / ledCount / stretch)
let reverse = true
basic.forever(function () {

const work = (offset:number)=>{
    if (displayTime() > 1000) basic.clearScreen()
    strip.setBrightness(maxb)

    const p = (i: number) => {

    }
    for (let i = 0; i < ledCount; i++) {
        let x = (gap * i) + offset
        let y = x >= hslElementCount ? x - hslElementCount : x
        let color = neopixel.hsl(y, 99, 10)
        strip.setPixelColor(i, color)
    }
    strip.show()
    basic.pause(speedOptions[speedIndex])
}

    if (reverse)
    {
        for (let offset = 0; offset < hslElementCount; offset++) {
            work(offset)
        }
    }
    else{
        for (let offset = hslElementCount; offset > 0; offset--) {
            work(offset)
        }
    }
    


})