var xT = 20;
var yT = 20;
var W = 500;
var H = 500;

var backgroundColor = "#F1F1F1";


tributary.init = function(ctx) {
};
tributary.run = function(ctx,t) {
    tributary.clear(); //helper function to clear the canvas

  	this.axisAndBackground(ctx);
};

//drawing functions

tributary.axisAndBackground = function(ctx){
  	ctx.fillStyle = backgroundColor;
  	this.drawRectT(ctx, 0, 0, 1, 1);

  	ctx.strokeStyle = 'black';
  	ctx.beginPath();
  	this.moveToT(ctx, 0,1);
  	this.lineToT(ctx, 0,0);
  	this.lineToT(ctx, 1,0);
  	ctx.stroke();
}



//drawing primitves

tributary.drawRectT = function(ctx, x, y, w, h){
  ctx.fillRect(x*W+xT, y*H+yT, w*W, h*H);
}
tributary.lineT = function(ctx, x0, y0, x1, y1){
  ctx.beginPath();
  this.moveToT(x0, y0);
  this.lineToT(x1, y1);
  ctx.stroke();
}
tributary.moveToT = function(ctx, x, y){
  ctx.moveTo(x*W+xT, (1-y)*H+yT);
}
tributary.lineToT = function(ctx, x, y){
  ctx.lineTo(x*W+xT, (1-y)*H+yT);
}