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HTML 

              
                    <header>
  <h1>touchpad input</h1>
</header>
<section>
  <div id="log">
    <p>X: <span id="xVal"></span></p>
    <p>Y: <span id="yVal"></span></p>
  </div>
  <div id="pad">
</div>
</section>
!

CSS 

              
                html {
  background: #232323;
}
* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
  font-family: sans-serif;
  font-weight: 300;
}
header {
  color: white;
  background: black;
  padding: 1rem;
}
section {
  padding: 2rem;
  display: grid;
  grid-template-columns: 120px 1fr;
}
#log {
  color: cyan;
  font-size: 2rem;
  font-weight: bold;
}
#yVal, #xVal {
  color: white;
  font-weight: light;
}
#pad {
  border: 2px solid black;
  width: 300px;
  height: 200px;
  background: #dcdadc;
}
!

JS 

              
                class TouchPad {
    private w: number = 200;
    private h: number = 200;
    private isPressed = false;
    private pos: TouchPad.coords = {x: 0, y: 0};
    private readonly marker = document.createElement('div');
    private readonly tracker = document.createElement('div');
    private readonly grid = document.createElement('div');
    private container: HTMLElement;
    private handler: (values: TouchPad.coords)=>void;

    constructor(
        containerID: string,
        onChange: (values: TouchPad.coords)=>void, 
        options: TouchPad.TouchPadOptions = {size: {w: 300, h: 200}, styles: {}, hideGrid: false}
    ) {
        const el = document.getElementById(containerID);
        if (!el) throw new Error('Invalid container ID');
        this.handler = onChange;
        this.container = el;
        this.initialize(options)
    }

    // Setup methods

    private initialize(options: TouchPad.TouchPadOptions) {

        if (options.size) {
            this.w = options.size.w;
            this.h = options.size.h;
            this.applyStyles(this.container, {
                width: `${this.w}px`,
                height: `${this.h}px`
            })
        }
        if (!options.hideGrid) {
            this.setupGrid()
        }
        this.connectDOM();
        this.setStyles(options.styles || {});
    }
    private setupGrid() {
        this.applyStyles(
            this.grid, 
            TouchPad.DEFAULT_STYLES.grid, {
                width: `${this.w}px`, 
                height: `${this.h}px`
            }
        );
        this.container.appendChild(this.grid);
    }
    private connectDOM() {
        this.container.appendChild(this.marker);
        this.container.appendChild(this.tracker);
        this.addEventListeners();
    }
    private addEventListeners() {
        this.container.addEventListener('mousedown', this.onMouseDown);
        this.container.addEventListener('mouseup', this.onMouseUp);
        this.container.addEventListener('pointerenter', this.onPointerEnter);
        this.container.addEventListener('pointerleave', this.onPointerLeave);
        this.container.addEventListener('mousemove', this.onMouseMove);
        window.addEventListener('mouseup', this.onMouseUp);
    }
    private setStyles(userStyles: Partial<CSSStyleDeclaration>) {
        this.applyStyles(
            this.container, 
            TouchPad.DEFAULT_STYLES.container, 
            userStyles, 
            {position: 'relative'}
        );
        this.applyStyles(this.marker, TouchPad.DEFAULT_STYLES.marker);
        this.applyStyles(this.tracker, TouchPad.DEFAULT_STYLES.tracker);
    }
    public destroy() {
        this.container.removeEventListener('mousedown', this.onMouseDown);
        this.container.removeEventListener('mouseup', this.onMouseUp);
        this.container.removeEventListener('pointerenter', this.onPointerEnter);
        this.container.removeEventListener('pointerleave', this.onPointerLeave);
        this.container.removeEventListener('mousemove', this.onMouseMove);
        window.removeEventListener('mouseup', this.onMouseUp);
    }


    // Event Handlers

    private onMouseDown = (e: MouseEvent) => {
        this.pos = this.getRelativeCoords(e);
        this.mark();
        this.isPressed = true;
    }
    private onMouseUp = (_e?: MouseEvent) => {
        this.isPressed = false;
    }
    private onMouseMove = (e: MouseEvent) => {
        const {x, y} = this.getRelativeCoords(e);
        if (this.containsPoint({x, y})) {
            this.tracker.style.opacity = '1';
            this.track({ x, y });
            if (this.isPressed) {
                this.pos = {x, y};
                this.mark()
            }
        } else {
            this.tracker.style.opacity = '0';
            this.isPressed = false;
        }
    }
    private onPointerEnter = () => {
        this.tracker.style.opacity = '1';
    }
    private onPointerLeave = () => {
        this.tracker.style.opacity = '0';
    }


    /** Returns the current value of the touchpad, {x, y}, both 0–1 relative to its size. */
    get value(): TouchPad.coords {
        return {
            x: TouchPad.percentOf(this.pos.x, this.w),
            y: TouchPad.percentOf(this.h - this.pos.y, this.h)
        };
    }

    // User feedback marker controls

    mark() {
        this.marker.style.top = `${this.pos.y}px`
        this.marker.style.left = `${this.pos.x}px`
        this.marker.style.opacity = '1';
        this.handler(this.value);
    }
    track({x, y}: TouchPad.coords) {
        this.tracker.style.top = `${y}px`
        this.tracker.style.left = `${x}px`
    }
    startTracking() {
        this.tracker.style.opacity = '1';
    }
    stopTracking() {
        this.tracker.style.opacity = '0';
    }

    // Helpers

    private getRelativeCoords(e: MouseEvent): TouchPad.coords {
        const rect = this.container.getBoundingClientRect();
        const x = Math.min(rect.width, Math.max(0, e.clientX - rect.left));
        const y = Math.min(rect.height, Math.max(0, e.clientY - rect.top));
        return { x, y };
    }

    private containsPoint({x, y}: TouchPad.coords) {
        const rect = this.container.getBoundingClientRect()
        return x >= 0 && y >= 0 && x <= rect.width && y <= rect.height
    }

    private applyStyles(el: HTMLElement, ...styles: Partial<CSSStyleDeclaration>[]) {
        Object.assign(el.style, ...styles);
    }

    static percentOf = (x: number, total: number) =>  Math.floor((x / total) * 100) / 100
}

namespace TouchPad {
    type touchpadElement = 'container' | 'grid' | 'marker' | 'tracker'
    export type StyleMap = Partial<CSSStyleDeclaration>;
    export type coords = { x: number, y: number };
    export type SizeType = { w: number, h: number };
    export type TouchPadOptions = {
        size?: SizeType,
        styles?: StyleMap,
        hideGrid?: boolean
    }
    export const DEFAULT_STYLES: Record<touchpadElement, StyleMap> = {
        container: {
            boxSizing: 'border-box',
            border: '2px solid #dddddd',
            backgroundImage: 'radial-gradient(circle at center, black, #181840)',
            overflow: 'hidden'
        },
        grid: {
            backgroundImage: 'linear-gradient(to right, #ffffff22 1px, transparent 1px), linear-gradient(to bottom, #ffffff22 1px, transparent 1px)',
            backgroundSize: '10% 10%, 10% 10%',
            zIndex: '2'
        },
        marker: {
            outline: '4px solid #ffffff55',
            background: 'cyan',
            opacity: '0',
            width: '15px',
            height: '15px',
            borderRadius: '50%',
            boxShadow: '0 0 20px 10px #000000aa',
            transform: 'translate(-50%, -50%)',
            position: 'absolute'
        },
        tracker: {
            background: '#ffffffaa',
            opacity: '0',
            filter: 'blur(20px)',
            width: '30px',
            height: '30px',
            borderRadius: '50%',
            transform: 'translate(-50%, -50%)',
            position: 'absolute'
        }
    }
}

const xVal = document.getElementById('xVal')!
const yVal = document.getElementById('yVal')!
const display = (values: TouchPad.coords) => {
    xVal.textContent = String(values.x);
    yVal.textContent = String(values.y);
}

const opts: TouchPad.TouchPadOptions = {
    size: {w: 350, h: 200}
}
const tp = new TouchPad('pad', (values)=>display(values), opts);
!
999px

Console