<!DOCTYPE html> <html> <!-- ahhh --> <body style="margin:0;overflow: hidden;"> <canvas id="myCanvas" width="10" height="10" style="display: block;box-sizing: border-box;"> Your browser does not support the HTML5 canvas tag.</canvas> <script> let c = document.getElementById("myCanvas"); let ctx = c.getContext("2d"); ctx.canvas.width = window.innerWidth; ctx.canvas.height = window.innerHeight; let deg_per_sec = 30; let time = 120; let fps = 60; centerX = ctx.canvas.width / 2; centerY = ctx.canvas.height / 2; rotation = 0; //was = j = angle currentFrame = 0; //was = i function render() { if (currentFrame < time / (1 / fps)) { setTimeout(() => { render(); render_clear(); draw_triangle(0, 200, "red"); }, 1000 / fps); rotation += deg_per_sec / fps; // was = j = angle, now = rotation currentFrame += 1; // was = i } } render(); function draw_triangle(ang, radius, colour) { ctx.beginPath(); ctx.moveTo(centerX + Math.cos(rad(90 + 120 * 1 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 1 + ang)) * radius); ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 2 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 2 + ang)) * radius); ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 3 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 3 + ang)) * radius); ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 1 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 1 + ang)) * radius); ctx.strokeStyle = colour; ctx.stroke(); } function rad(degrees) { var pi = Math.PI; return degrees * (pi / 180); } function render_clear() { ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); ctx.fillStyle = "black"; ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height); } </script> </body> </html>