# Líneas que se mueven — How to move a line across the sketch
**URL:** https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413
**Category:** Español
**Tags:** homework
**Created:** [January 2, 2023, 6:26pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413 "2023-01-02T18:26:12Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@paopoapo](https://discourse.processing.org/u/paopoapo)
#### Post date: [January 2, 2023, 6:26pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/1 "2023-01-02T18:26:12Z")
> please format code with \ button \* [homework policy](https://discourse.processing.org/faq/#homework) \* [asking questions](https://discourse.processing.org/t/2147)
hola,
me mandaron un ejercicio y no se cómo hacerlo
dice
líneas de distintos colores que aparecen de un extremo a otro de la pantalla
---
### Author:  [@svan](https://discourse.processing.org/u/svan)
#### Post date: [January 2, 2023, 7:32pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/2 "2023-01-02T19:32:46Z")
This reference shows how to draw a line:[https://processing.org/reference/line\_.html](https://processing.org/reference/line_.html)
---
### Author:  [@debxyz](https://discourse.processing.org/u/debxyz)
#### Post date: [January 2, 2023, 8:13pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/3 "2023-01-02T20:13:40Z")
Hello @paopoapo
**The exercise: lines of different colors that appear from one end of the screen to the other**
Break down your problem into small steps.
You will need:
1/ to make a random color for each new line
2/ to make a lot of lines
3/ fill the screen with the lines
In the processing reference look up:
line()
color()
random()
Please tell us what you know, or share your code. Then we can give you more specific guidance.
🤓
---
### Author:  [@paopoapo](https://discourse.processing.org/u/paopoapo)
#### Post date: [January 2, 2023, 8:35pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/4 "2023-01-02T20:35:15Z")
y cómo sería el código para hacer esos 3 pasos ?
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### Author:  [@debxyz](https://discourse.processing.org/u/debxyz)
#### Post date: [January 2, 2023, 8:46pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/5 "2023-01-02T20:46:48Z")
Since this is a homework assignment, I’m not going to do that for you. You won’t learn anything.
I gave you a very specific roadmap.
The next step is to read the reference entries and write some code.
After that, if you have any questions, come back and I will help you.
🤓
---
### Author:  [@paopoapo](https://discourse.processing.org/u/paopoapo)
#### Post date: [January 3, 2023, 3:45pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/6 "2023-01-03T15:45:58Z")
esto es lo que tengo pero necesito que no se salgan de la pantalla sino que choquen de lado a lado y que sean de diferentes colores
final int nbOfLines = 50;
ArrayList lines;
void setup() {
size(900, 900);
frameRate(60);
lines = new ArrayList();
createLines();
}
void draw() {
background(20);
for (int i = 0; i \< lines.size(); i++) {
lines.get(i).run();
}
if (lines.get(lines.size() - 1).isOutOfScreen()) {
createLines();
}
}
void createLines() {
lines.clear();
int y = height;
for (int i = 0; i \< nbOfLines; i++) {
y += random(10) + 1;
lines.add(new CustomLine(y));
}
}
class CustomLine {
private int y;
CustomLine(int y) {
this.y = y;
}
void run() {
move();
display();
}
void move() {
y -= 2;
}
void display() {
stroke(200);
line(0, y, width, y);
}
boolean isOutOfScreen() {
return y \< 0;
}
}
---
### Author:  [@debxyz](https://discourse.processing.org/u/debxyz)
#### Post date: [January 3, 2023, 5:29pm UTC](https://discourse.processing.org/t/lineas-que-se-mueven-how-to-move-a-line-across-the-sketch/40413/7 "2023-01-03T17:29:44Z")
> [@paopoapo](#):
>
> esto es lo que tengo pero necesito que no se salgan de la pantalla sino que choquen de lado a lado y que sean de diferentes colores
This is what I have but I need them not to go off the screen but to collide from side to side and to be different colors.
///////////////////////////////////////////////////////////////////////
See the comments next to the lines I have added and/or changed.
I hope this helps!
////////////////////////////////////////////////////////
Your code with alterations in place:
```auto
final int nbOfLines = 50;
ArrayList lines; // declare the CustomLine class
void setup() {
size(900, 900);
frameRate(60);
lines = new ArrayList();
createLines();
}
void draw() {
background(20);
for (int i = 0; i < lines.size(); i++) {
lines.get(i).run();
}
//if (lines.get(lines.size() - 1).isOutOfScreen()) {
// createLines();
//}
}
void createLines() {
lines.clear();
int y = 0; // begin lines from top of screen
for (int i = 0; i < nbOfLines; i++) {
y += 10;
lines.add(new CustomLine(y));
}
}
class CustomLine {
private int y;
int ySpeed = 5; // add speed variable to move the lines
color col = color(random(255), random(255), random(255)); //declare your colors here
CustomLine(int y) {
this.y = y;
}
void run() {
bounce(); // call bounce function
move();
display();
}
void move() {
y = y + ySpeed;
}
void bounce() { // add bounce function
if (y > height || y < 0) { // if y is greater than height, or y is less than "0"
ySpeed = ySpeed * -1; // change direction
}
}
void display() {
stroke(col);
line(0, y, width, y);
}
//boolean isOutOfScreen() { // do not need this boolean, it changes the line bounce behavior
// return y < 0;
//}
}
```
🤓