Pong in R

pong.R

# remotes::install_github("coolbutuseless/eventloop")

Pong <- R6::R6Class(
  "pong",
  
  public = list(
    initialize = function(width=10, height=7, speed=0.02) {
      require(grid)
      private$width <- width
      private$height <- height
      private$speed <- speed
      private$respawn()
    },
    
    play = function() {
      eventloop::run_loop(private$loop, NULL, private$width, private$height)
    }
  ),
  
  private = list(
    width = NULL,
    height = NULL,
    speed = NULL,
    pos = NULL,
    angle = NULL,
    ball.r = 0.03,
    pad.r = 0.1,
    p.points = c(0, 0),
    p.y = c(0.5, 0.5),
    
    loop = function(event, ...) {
      private$move_ball()
      private$move_pads(event)
      
      grid.rect(gp=gpar(fill="black"))
      grid.lines(c(0.5, 0.5), c(0, 1), gp=gpar(col="white", lty="dashed"))
      grid.circle(private$pos[1], private$pos[2], private$ball.r, gp=gpar(fill="white"))
      grid.rect(0, private$p.y[1], 0.02, 2*private$pad.r, gp=gpar(fill="white"))
      grid.rect(1, private$p.y[2], 0.02, 2*private$pad.r, gp=gpar(fill="white"))
      grid.text(private$p.points[1], 0.45, 0.95, gp=gpar(col="white", fontsize=30))
      grid.text(private$p.points[2], 0.55, 0.95, gp=gpar(col="white", fontsize=30))
    },
    
    respawn = function(scored) {
      if (!missing(scored))
        private$p.points[scored] <- private$p.points[scored] + 1
      private$pos <- c(0.5, runif(1))
      private$angle <- runif(1, -pi/4, pi/4) + sample(c(0, pi), 1)
    },
    
    move_ball = function() {
      private$pos <- private$pos + c(cos(private$angle), sin(private$angle)) * private$speed
      
      # x bounce or score
      if (private$pos[1] <= private$ball.r) {
        if (private$pos[2] <= private$p.y[1] + private$pad.r && 
            private$pos[2] >= private$p.y[1] - private$pad.r) {
          private$pos[1] <- private$ball.r
          private$angle <- pi - private$angle
        } else private$respawn(2)
      } else if (private$pos[1] >= 1 - private$ball.r) {
        if (private$pos[2] <= private$p.y[2] + private$pad.r && 
            private$pos[2] >= private$p.y[2] - private$pad.r) {
          private$pos[1] <- 1 - private$ball.r
          private$angle <- pi - private$angle
        } else private$respawn(1)
      }
      
      # y bounce
      if (private$pos[2] <= private$ball.r) {
        private$pos[2] <- private$ball.r
        private$angle <- 2*pi - private$angle
      } else if (private$pos[2] >= 1 - private$ball.r) {
        private$pos[2] <- 1 - private$ball.r
        private$angle <- 2*pi - private$angle
      }
      
      # normalize angle
      private$angle <- private$angle - private$angle %/% (2*pi) * 2*pi
    },
    
    move_pads = function(event) {
      if (!is.null(event) && event$type == "key_press") {
        # player 2
        if (event$str == "Up" && private$p.y[2] < 1 - private$pad.r) {
          private$p.y[2] <- private$p.y[2] + 2 * private$speed
        } else if (event$str == "Down" && private$p.y[2] > private$pad.r) {
          private$p.y[2] <- private$p.y[2] - 2 * private$speed
        }
        # player 1
        if (event$str == "w" && private$p.y[1] < 1 - private$pad.r) {
          private$p.y[1] <- private$p.y[1] + 2 * private$speed
        } else if (event$str == "s" && private$p.y[1] > private$pad.r) {
          private$p.y[1] <- private$p.y[1] - 2 * private$speed
        }
      }
    }
  )
)

Pong$new()$play()