JSFiddle - React, Tailwind, and code Playground

HTML

<p>ここにマウスで描けます</p>
		<canvas></canvas>

CSS

canvas {
  background:#fff;
				width: 100vw;
				height: 100vh;
				position: fixed;
				top: 0;
				left: 0;
				z-index: 2;
			}
			p {
				z-index: 3;
				position: fixed;
				top: 300;
				left: 100;
				background: rgba(0, 0, 0, 0.7);
				padding: 1em;
				color:white;
			}
			form * {
				margin-bottom: 1em;
			}

JavaScript

"use strict";
var _createClass = function() {
    function defineProperties(target, props) {
        for (var i = 0; i < props.length; i++) {
            var descriptor = props[i];
            descriptor.enumerable = descriptor.enumerable || false;
            descriptor.configurable = true;
            if ("value" in descriptor) descriptor.writable = true;
            Object.defineProperty(target, descriptor.key, descriptor)
        }
    }
    return function(Constructor, protoProps, staticProps) {
        if (protoProps) defineProperties(Constructor.prototype, protoProps);
        if (staticProps) defineProperties(Constructor, staticProps);
        return Constructor
    }
}();

function _possibleConstructorReturn(self, call) {
    if (!self) {
        throw new ReferenceError("this hasn't been initialised - super() hasn't been called")
    }
    return call && (typeof call === "object" || typeof call === "function") ? call : self
}
function _inherits(subClass, superClass) {
    if (typeof superClass !== "function" && superClass !== null) {
        throw new TypeError("Super expression must either be null or a function, not " + typeof superClass)
    }
    subClass.prototype = Object.create(superClass && superClass.prototype, {
        constructor: {
            value: subClass,
            enumerable: false,
            writable: true,
            configurable: true
        }
    });
    if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass
}
function _classCallCheck(instance, Constructor) {
    if (!(instance instanceof Constructor)) {
        throw new TypeError("Cannot call a class as a function")
    }
}
var Point = function() {
    function Point(x, y) {
        _classCallCheck(this, Point);
        if (arguments.length < 2) throw new Error("not enough coordinates for Point.");
        this._x = x;
        this._y = y
    }
    _createClass(Point, [{
        key: "set",
        value:...