Scratch To Unity: Sensing

Beginner Scratch Tutorial Unity

This post provides a handy reference guide to go from Scratch’s “Sensing” category of code blocks to C# with Unity.

Earth Day (Ahem, Earth Week)
Wednesday April 24, 2019

We’re doing a giveaway! Earth Day 2019 has passed, but we’re extending our earth-friendly efforts all week long. On Monday, we held an Earth Day event on campus to encourage the LAFS community to clean up Hollywood. Thank you to all of those who participated and showed their support for our planet. While there are […]

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Code Blocks
Click on the picture of any of these Scratch code blocks to see how to write similar code statements in C#.

Universities in Munich
Monday December 17, 2018

The Technical University of Munich (shortly referred to as TUM) is regularly ranked amongst the world’s top 100 universities, but there are a lot more universities in Munich which are of a similar quality. Their position at the top of the international education market is actually not an accident. These universities offer limitless study options […]

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void OnMouseOver()
// Code to run when mouse is touching

The Physics engine in Unity is not based on pixel color. It is based on Collider shapes. You can mask collisions to control what collides with what, or wait for a collision and then check properties of the objects in the relevant callbacks:

void OnCollisionEnter(Collision collision)
// Check "color" of objects

Phd in Germany
Wednesday October 24, 2018

PhD studies are the uppermost level of education and the final stamp of your academic competence in a particular study field. Valued among global leaders on research activities, for the quality of education and academic staff, modern facilities and associated infrastructure for scientific work, and most importantly for future prosperity that it produces, Germany is […]

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Assuming an object is in screen space coordinates, like a UI Element, then you could use something like this:

var distance = Vector3.Distance(transform.position, Input.mousePosition);

See the “Motion” reference guide for examples of ray casting from the mouse position into the 3D world.

There is no built-in equivalent to this code block, but you can make your own. From the Hierarchy pane click the “Create” button and choose “UI” -> “Input Field”. You can add a handler method to the “On End Edit” event either in the Inspector or in code.
To work with an Input Field in code you must add the using declaration:

using UnityEngine.UI;

Here is an example of attaching a handler to the “On End Edit” event:

private void Start()
var input = GetComponent<InputField>();

void OnEndEdit(string result)

if (Input.GetKey(KeyCode.Space))
// Code to run when key is pressed

if (Input.GetMouseButton(0))
// Code to run when mouse button is pressed

var mouseX = Input.mousePosition.x;

var mouseY = Input.mousePosition.y;

Unity does not provide a built-in solution for dragging objects with the mouse. You can create your own by detecting mouse events and moving objects based on “Input.mousePosition”. If you create a component to handle dragging, then you can disable dragging by disabling the component.

In Unity, there is no exposed “loudness” variable. You have “volume” on “AudioSource” components, but that is how loud to play the clip as a whole, not how loud is the sound that is actually being heard. In other words, imagine you have turned the volume knob of a speaker all the way up. When sound plays, it will be loud, but there may be moments between sounds where there is nothing to hear.
In order to analyze the loudness of what is actually playing, you can sample your audio data. Here is a post on the Unity Answers forum that discusses this topic in detail, complete with code.

Unity does not have a built-in timer. You can track the passing of time using the “Time” class. See here. A simple timer might look something like this.

float timer = 10f;

void Update()
if (timer > 0)
timer -= Time.deltaTime;
if (timer <= 0)
Debug.Log("Time's up!");

Backdrops are not special entities in Unity. You could create one as a Sprite just like you would create any other sprite. If you had a collection of backgrounds to use, then you could track the index of the background when you assign it on your own.

To work with date data types, you will need to add a using declaration:

using System;

You can then obtain the current year like this:

var currentDate = DateTime.Now;
var year = currentDate.Year;

To work with date data types, you will need to add a using declaration:

using System;

You can then obtain the number of days since 2000 like this:

var oldDate = new DateTime(2000, 1, 1);
var currentDate = DateTime.Now;
var totalDays = (currentDate – oldDate).TotalDays;

There is no equivalent to a username built-in to Unity. This is an advanced task that requires a server to implement. You might wish to pursue 3rd party libraries for this purpose such as Firebase.
This should cover all of the code blocks in Scratch’s “Sensing” category. If you have any questions about this reference guide feel free to ask below.
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