Character Select

can anyone explain to me how to make a character select screen? (to select, use left and right controls)

You need to control the draw, update loop. Let only one object have access to the screen keyboard and update .

ControlLoop = class
  constructor = function( call )
    setCall( call )
  end
  draw = function() 
    screen.clear("purple")
  end
  update = function() 
    if keyboard.press.SPACE then 
      return this.call 
    else 
      return this 
    end  
  end
  setCall = function( call )
    this.call = call
  end
end

Select = class extends ControlLoop
  constructor = function( call )
    super( call )
    this.select = 0
  end
  
  draw = function()
    screen.clear("orange")
    screen.drawText( "LEFT RIGHT to select", 0 , 70, 30, "black")
    screen.fillRect( -50, 0, 50, 100, "red")
    screen.fillRect( 50, 0, 50, 100, "green")
    screen.drawRect( 100 * this.select -50, 0, 60, 110 )
    screen.drawText( " SPACE to EXIT ", 0, -70, 30, "black")
  end
  
  update = function()
    if keyboard.press.LEFT then 
      this.select = 0
    elsif keyboard.press.RIGHT then 
      this.select = 1
    end    
    return super()
  end
end

Game = class extends ControlLoop
  constructor = function()
    select = new Select( this )
  end
  draw = function()
    screen.clear("blue")
    screen.drawText(" You select " + select.select, 0, 0, 30, "white" )
    screen.drawText(" Press SPACE to select", 0, -40, 40, "orange" )  
  end
  update = function()
    if keyboard.press.SPACE then 
      audio.beep("C")
      return select
    else
      return this
    end
  end
end

init = function()
  game = new Game()
  current = game 
end

update = function()
  current = current.update()
end

draw = function()
  current.draw()
end

I suggest using different scene classes with own update and draw functions. We will have scene pointer to the current scene and you can change the current scene at any time assigning any scene to the pointer:

scene = selectionScene

scene = playingScene

scene = gameOverScene

The selection logic is contained in SelectionScene.update function and corresponding rendering in SelectionScene.draw. The other two scenes are provided as examples of data exchange between scenes and, again, scene switching

//list the hero selection sprites
local heroSprites = ["sprite_a", "sprite_b", "sprite_c"]
//define the hero count
local heroesCount = heroSprites.length


SelectionScene = class
  selection = 0
  
  update = function()
    if keyboard.press.LEFT then
      selection = selection - 1
    end
    
    if keyboard.press.RIGHT then
      selection = selection + 1
    end
    
    if selection < 0 then
      selection = heroesCount - 1
    elsif selection >= heroesCount then
      selection = 0
    end
    
    if keyboard.press.SPACE then
      playingScene.restart(selection)
      global.scene = playingScene
    end
  end

  draw = function()
    screen.clear()
    local shift = -(heroesCount - 1) * 40 * 0.5
    
    for i = 0 to heroesCount - 1
      screen.drawSprite(heroSprites[i], i * (40) + shift, 0)
    end
    
    screen.drawRect(shift + selection * 40, 0, 40, 40)
  end
end

PlayingScene = class
  restart = function(i)
    this.i = i
    t = 0
  end
  
  update = function()
    t = t + 1
    if t >= 180 then
      global.scene = gameOverScene
    end
  end
  
  draw = function()
    screen.clear()
    screen.drawSprite(heroSprites[i], 0, 0)
    screen.drawText(t + "/180", 0,-30, 16)
  end
end

GameOverScene = class
  update = function()
    if keyboard.press.SPACE then
      playingScene.restart(selection)
      global.scene = selectionScene
    end
  end
  
  draw = function()
    screen.clear()
    screen.drawText("Game Over", 0, 10, 16)
    screen.drawText("Press SPACE to continue", 0, -10, 16)
  end
end


//all the scenes
selectionScene = new SelectionScene()
playingScene = new PlayingScene()
gameOverScene = new GameOverScene()


//currentScene
scene = selectionScene


update = function()
  //update current scene
  scene.update()
end

draw = function()
  //draw current scene
  scene.draw()
end