Pong Wars

Two seconds into a video of this little game, I just knew I had to build it for myself.

local n = 20  -- px per square
local v = 200  -- ball velocity in px/s
-- initialize a w*h board randomly with one of 2 states
local w = floor((Safe_width-60)/n)
local h = floor(Safe_height/2/n)
local board = {}
for y=1,h do
  local row = {}
  for x=1,w do
    table.insert(row, rand(1,2))
  end
  table.insert(board, row)
end
local px = (Safe_width-n*w)/2
-- initialize colors for the 2 states
local c1 = {0.8, 0.8, 1}
local c2 = {0.8, 0.9, 0.8}
colors = {c1, c2}
-- initialize 2 balls
local b1 = {x=0, y=floor(n*h/2)}
local b2 = {x=n*w, y=floor(n*h/2)}
balls = {b1, b2}  -- region color to ball within it
-- give each ball a unit velocity in a random direction
function randNorm2()
  local p = {x=rand(-100,100), y=rand(-100,100)}
  local m = math.sqrt(p.x^2 + p.y^2)
  return {x=p.x/m, y=p.y/m}
end
b1.v = randNorm2()
b2.v = randNorm2()
function car.draw()
  for y=1,h do
    for x=1,w do
      color(unpack(colors[board[y][x]]))
      rect('fill', px+(x-1)*n, Menu_bottom+(y-1)*n, n,n)
    end
  end
  color(unpack(c2))
  circle('fill', px+balls[1].x, Menu_bottom+balls[1].y, n/2)
  color(unpack(c1))
  circle('fill', px+balls[2].x, Menu_bottom+balls[2].y, n/2)
end
function car.update(dt)
  for c,b in ipairs(balls) do
    if b.v.x < 0 and (b.x < 1/2*n or maybe_set_board(b.x-1/2*n, b.y, c)) then
      b.v.x = abs(b.v.x)
    elseif b.v.x > 0 and (b.x > (w-1/2)*n or maybe_set_board(b.x+1/2*n, b.y, c)) then
      b.v.x = -abs(b.v.x)
    elseif b.v.y < 0 and (b.y < 1/2*n or maybe_set_board(b.x, b.y-1/2*n, c)) then
      b.v.y = abs(b.v.y)
    elseif b.v.y > 0 and (b.y > (h-1/2)*n or maybe_set_board(b.x, b.y+1/2*n, c)) then
      b.v.y = -abs(b.v.y)
    end
    b.x = b.x + v*b.v.x*dt
    b.y = b.y + v*b.v.y*dt
  end
end
function maybe_set_board(x, y, c)
  x, y = s(x), s(y)
  if board[y][x] == c then return end
  board[y][x] = c
  return true
end
function s(z) return 1+floor(z/n) end

If you try pasting this program into Lua Carousel, remember to first run the abbreviations on one of the example screens. Or if you've deleted that screen, here are the abbreviations I used in this post:

g = love.graphics
rect, circle = g.rectangle, g.circle
color = g.setColor
floor, ceil = math.floor, math.ceil
abs, rand = math.abs, math.random

Credits

• https://twitter.com/CasualEffects/status/1390290306206216196
• https://hachyderm.io/@bazzargh/111829275276749971
• https://hachyderm.io/@vnglst/111828811496422610
• https://pong-wars.koenvangilst.nl