jamolkhon/gist:fb8c769390ad56241d8abb8e5129da84

## gistfile1.txt
package com.mygdx.game

import com.badlogic.gdx.Gdx
import com.badlogic.gdx.InputAdapter
import com.badlogic.gdx.Screen
import com.badlogic.gdx.ScreenAdapter
import com.badlogic.gdx.graphics.GL20
import com.badlogic.gdx.graphics.OrthographicCamera
import com.badlogic.gdx.math.Vector2
import com.badlogic.gdx.physics.box2d.*
import com.badlogic.gdx.utils.Array

class GameScreen : Screen by ScreenAdapter() {

  private val camera = OrthographicCamera().apply { setToOrtho(false) }

  private val world = World(Vector2.Zero, true)

  private val renderer = Box2DDebugRenderer()

  init {
    walls()
    balls()

Gdx.input.inputProcessor = object : InputAdapter() {
      override fun keyUp(keycode: Int): Boolean {
        Gdx.app.log("GameScreen", "applying impulse")
        val bodies = Array<Body>()
        world.getBodies(bodies)
        if (bodies.notEmpty()) {
          val body = bodies[0]
          body.applyLinearImpulse(Vector2(1f.unit, 1f.unit), body.worldCenter, true)
        }
        return true
      }
    }
  }

  override fun resize(width: Int, height: Int) {
  }

  override fun render(delta: Float) {
    camera.update()
    Gdx.gl.glClearColor(0f, 0f, 0f, 1f)
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT)
    world.step(1 / 60f, 6, 2)
    renderer.render(world, camera.combined.scale(100f, 100f, 0f))
  }

  private fun walls() {
    val bodyDef = BodyDef().apply {
      type = BodyDef.BodyType.StaticBody
      position.setZero()
    }

    val chainShape = ChainShape()
    chainShape.createChain(arrayOf(
        Vector2(10f.unit, 10f.unit),
        Vector2(300f.unit, 10f.unit),
        Vector2(300f.unit, 500f.unit),
        Vector2(10f.unit, 500f.unit),
        Vector2(10f.unit, 10f.unit)))

    val fixtureDef = FixtureDef().apply {
      shape = chainShape
      friction = 1f
      restitution = 1f
    }

    world.createBody(bodyDef).createFixture(fixtureDef)
    chainShape.dispose()
  }

  private fun balls() {
    val bodyDef = BodyDef().apply {
      type = BodyDef.BodyType.DynamicBody
      fixedRotation = true
      linearDamping = 0.5f
      angularDamping = 0.5f
      position.set(30f.unit, 30f.unit)
    }

    val circleShape = CircleShape().apply {
      position.setZero()
      radius = 10f.unit
    }
    val fixtureDef = FixtureDef().apply {
      shape = circleShape
      friction = 0f
      restitution = 0f
      density = 0.1f
    }

    body = world.createBody(bodyDef).apply { createFixture(fixtureDef) }
    circleShape.dispose()
  }

  override fun dispose() {
  }
}
	package com.mygdx.game

	import com.badlogic.gdx.Gdx
	import com.badlogic.gdx.InputAdapter
	import com.badlogic.gdx.Screen
	import com.badlogic.gdx.ScreenAdapter
	import com.badlogic.gdx.graphics.GL20
	import com.badlogic.gdx.graphics.OrthographicCamera
	import com.badlogic.gdx.math.Vector2
	import com.badlogic.gdx.physics.box2d.*
	import com.badlogic.gdx.utils.Array

	class GameScreen : Screen by ScreenAdapter() {

	private val camera = OrthographicCamera().apply { setToOrtho(false) }

	private val world = World(Vector2.Zero, true)

	private val renderer = Box2DDebugRenderer()

	init {
	walls()
	balls()

	Gdx.input.inputProcessor = object : InputAdapter() {
	override fun keyUp(keycode: Int): Boolean {
	Gdx.app.log("GameScreen", "applying impulse")
	val bodies = Array<Body>()
	world.getBodies(bodies)
	if (bodies.notEmpty()) {
	val body = bodies[0]
	body.applyLinearImpulse(Vector2(1f.unit, 1f.unit), body.worldCenter, true)
	}
	return true
	}
	}
	}

	override fun resize(width: Int, height: Int) {
	}

	override fun render(delta: Float) {
	camera.update()
	Gdx.gl.glClearColor(0f, 0f, 0f, 1f)
	Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT)
	world.step(1 / 60f, 6, 2)
	renderer.render(world, camera.combined.scale(100f, 100f, 0f))
	}

	private fun walls() {
	val bodyDef = BodyDef().apply {
	type = BodyDef.BodyType.StaticBody
	position.setZero()
	}

	val chainShape = ChainShape()
	chainShape.createChain(arrayOf(
	Vector2(10f.unit, 10f.unit),
	Vector2(300f.unit, 10f.unit),
	Vector2(300f.unit, 500f.unit),
	Vector2(10f.unit, 500f.unit),
	Vector2(10f.unit, 10f.unit)))

	val fixtureDef = FixtureDef().apply {
	shape = chainShape
	friction = 1f
	restitution = 1f
	}

	world.createBody(bodyDef).createFixture(fixtureDef)
	chainShape.dispose()
	}

	private fun balls() {
	val bodyDef = BodyDef().apply {
	type = BodyDef.BodyType.DynamicBody
	fixedRotation = true
	linearDamping = 0.5f
	angularDamping = 0.5f
	position.set(30f.unit, 30f.unit)
	}

	val circleShape = CircleShape().apply {
	position.setZero()
	radius = 10f.unit
	}
	val fixtureDef = FixtureDef().apply {
	shape = circleShape
	friction = 0f
	restitution = 0f
	density = 0.1f
	}

	body = world.createBody(bodyDef).apply { createFixture(fixtureDef) }
	circleShape.dispose()
	}

	override fun dispose() {
	}
	}