feat: canvas based interactive background

web/bg.js

@@ -0,0 +1,57 @@
+const COLOR_SURFACE1 = "#dce0e8";
+const DOT_RADIUS = 1 * devicePixelRatio;
+
+const canvas = document.getElementById("bg");
+const ctx = canvas.getContext("2d");
+
+let mouseX = 0;
+let mouseY = 0;
+
+function resizeCanvas(width, height) {
+	const devicePixelRatio = window.devicePixelRatio || 1;
+	canvas.style.width = `${width}px`;
+	canvas.style.height = `${height}px`;
+	canvas.width = width * devicePixelRatio;
+	canvas.height = height * devicePixelRatio;
+}
+
+function clearCanvas() {
+	ctx.clearRect(0, 0, canvas.width, canvas.height);
+}
+
+function drawDot(x, y) {
+	const distance = Math.sqrt((x - mouseX) ** 2 + (y - mouseY) ** 2);
+	const effectRadius = 100;
+	const radius =
+		DOT_RADIUS +
+		2 *
+			devicePixelRatio *
+			((effectRadius - Math.min(distance, effectRadius)) / effectRadius);
+	ctx.beginPath();
+	ctx.arc(x, y, radius, 0, 2 * Math.PI, false);
+	ctx.fillStyle = COLOR_SURFACE1;
+	ctx.fill();
+}
+
+function drawPattern() {
+	clearCanvas();
+	for (let x = 0; x < canvas.width; x += 10 * devicePixelRatio) {
+		for (let y = 0; y < canvas.height; y += 10 * devicePixelRatio) {
+			drawDot(x, y);
+		}
+	}
+}
+
+window.addEventListener("resize", () => {
+	resizeCanvas(window.innerWidth, window.innerHeight);
+	drawPattern();
+});
+
+window.addEventListener("mousemove", (event) => {
+	mouseX = event.clientX * devicePixelRatio;
+	mouseY = event.clientY * devicePixelRatio;
+	drawPattern();
+});
+
+resizeCanvas(window.innerWidth, window.innerHeight);
+drawPattern();