shape.camp/client/src/components/Game.js

import React from "react";
import Sketch from "react-p5";

let positions = [];

let initialPos;
let playerPath = [];

let stepX;
let stepY;
let numCols = 50;
let numRows = 25;

export default (props) => {
    const setup = (p5, canvasParentRef) => {
        p5.createCanvas(1000, 500).parent(canvasParentRef);

        const setupGrid = () => {
            stepX = p5.width / numCols; //to make sure they are evenly spaced, we divide the width and height by numberOfColumns
            stepY = p5.height / numRows; //and numberOfRows respectively

            for (let x = 0; x < p5.width; x += stepX) {
                //start at the first column, where x = 0

                for (let y = 0; y < p5.height; y += stepY) {
                    //go through all the rows (y = 0, y = yStep * 1, y  = yStep * 2, etc.)

                    const p = p5.createVector(x, y); //we create a vector at this location

                    positions.push(p); // and then we put the vector into the array
                }
                //at the end of the inner for loop, we go back to the first loop, and we increment x
                //now our column is going to b x = xStep*1, and we populate all the rows with the inner for loop
                //and again, and again until x > width
            }
        };

        const setupPlayer = () => {
            initialPos = p5.createVector(5, 5);
            playerPath.push(p5.createVector(1, 0));
            playerPath.push(p5.createVector(1, 1));
            playerPath.push(p5.createVector(1, 1));
            playerPath.push(p5.createVector(0, 1));
        };

        setupGrid();
        setupPlayer();
    };

    const draw = (p5) => {
        const drawGrid = () => {
            p5.push();

            p5.fill(100, 100, 100);
            p5.noStroke();

            for (let i = 0; i < positions.length; i++) {
                //go through all our positions
                p5.ellipse(positions[i].x, positions[i].y, 2, 2); //put a circle at each of them
            }

            p5.pop();
        };

        const drawPlayer = () => {
            p5.push();

            p5.fill(255, 0, 0); // Red

            p5.noStroke();

            // Need to clone here to not override initial position
            let currentPos = { ...initialPos };

            // Draw initial position
            p5.ellipse(currentPos.x * stepX, currentPos.y * stepY, 5, 5);

            for (let pos of playerPath) {

                const previous = { ...currentPos };

                currentPos.x += pos.x;
                currentPos.y += pos.y;

                p5.push();
                p5.stroke(150);
                p5.line(previous.x * stepX, previous.y * stepY, currentPos.x * stepX, currentPos.y * stepY);
                p5.pop();

                p5.ellipse(currentPos.x * stepX, currentPos.y * stepY, 5, 5);
            }

            p5.pop();
        };

        drawGrid();
        drawPlayer();
    };

    return <Sketch setup={setup} draw={draw} />;
};