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                    // This file demonstrates to change dynamically properties of an object.
    // Each time the window is refreshed, a red or blue light dot is drawn on the circumference.

    const jsPsych = initJsPsych({
        on_finish: function() {

    const pixi_flag ='pixi_flag') === '1' ? true : false;

    const instruction = {
        type: jsPsychHtmlButtonResponse,
        stimulus: 'Click on the Start button.',
        choices: ['Start'],
        prompt: "This is a sample program for the jspsych-psychophysics plugin."

    const radius = 200
    let theta_in_radian = 2 * Math.PI * Math.random()

    const dot_object = {
        obj_type: 'circle',
        radius: 20, // radius of the dot
        origin_center: true,
        startX : function(){
            return radius * Math.cos(theta_in_radian)
        startY : function(){
            return radius * Math.sin(theta_in_radian)
        width: 200,
        height: 50,
        fill_color: function(){
            if (Math.random() < 0.5){
                return 'blue'
            } else {
                return 'red'
        show_start_time: function(){
            const min = 700
            return min + Math.random()*500

    const circle_object = {
        obj_type: 'circle',
        radius: radius,
        line_color: 'black'

    const trial = {
        type: jsPsychPsychophysics,
        pixi: pixi_flag,
        stimuli: [dot_object, circle_object],
        response_type: 'button',
        canvas_height: 500,
        prompt: `Each time you press the "Next" button, the position and color of the circle will change.`

    const loop_node = {
        timeline: [trial],
        loop_function: function(data){
            theta_in_radian = 2 * Math.PI * Math.random()
            return true
    }[instruction, loop_node])