Create a sine-based "hill" with configurable parameters.

sineHill.js

var ctx = canvas.getContext('2d');
    
var iterations = 15,
	moveX = 10,
	amp = 80,
	startX = 200, startY = 200,
	i, rad, ny;

ctx.beginPath();
ctx.moveTo(startX, startY);

for (i = 1; i <= iterations; i++) {
	rad = Math.PI/iterations * i;
	ny = Math.sin(rad) * -amp;
    
	ctx.lineTo(startX + moveX*i, startY + ny);
}

ctx.stroke();