lua moving ball

lua-moving-ball/main.lua

@@ -0,0 +1,100 @@
+-- Gist accompanying https://alloca.space/blog/lua-lang.html
+--
+-- Build and Run
+-- -------------
+--
+-- 1. Install https://love2d.org on your system
+--
+-- 2. Run with:
+--
+--    love .
+
+
+-- Constants
+
+SCREEN_WIDTH = 640
+SCREEN_HEIGHT = 480
+BALL_SPEED = 200
+BALL_RADIUS = 50
+
+-- Objects
+
+local background = {
+   ["color"] = {
+      ["r"] = 0x08 / 255,
+      ["g"] = 0x18 / 255,
+      ["b"] = 0x29 / 255,
+   }
+}
+
+local ball = {
+   position = {
+      ["x"] = SCREEN_WIDTH/3,
+      ["y"] = SCREEN_HEIGHT/3,
+   },
+   direction = {
+      ["x"] = 1,
+      ["y"] = 1,
+   },
+   color = {
+      ["r"] = 0xf9 / 255,
+      ["g"] = 0x92 / 255,
+      ["b"] = 0x26 / 255,
+   },
+   ["radius"] = BALL_RADIUS,
+}
+
+-- Main
+
+function love.load()
+   love.window.setMode(SCREEN_WIDTH, SCREEN_HEIGHT, {vsync=true,msaa=4})
+end
+
+function love.update()
+   updateBall(ball)
+end
+
+function love.draw()
+   love.graphics.clear(background.color.r, background.color.g, background.color.b, 255, true, true)
+
+   love.graphics.setColor(ball.color.r, ball.color.g, ball.color.b)
+   love.graphics.circle("fill", ball.position.x, ball.position.y, ball.radius)
+end
+
+-- Update
+
+function updateBall(ball)
+   applyKeys(ball)
+   swingBall(ball)
+end
+
+function applyKeys(ball)
+   if love.keyboard.isDown("d") then ball.direction.x = 1 end
+   if love.keyboard.isDown("a") then ball.direction.x = -1 end
+   if love.keyboard.isDown("s") then ball.direction.y = 1 end
+   if love.keyboard.isDown("w") then ball.direction.y = -1 end
+end
+
+function swingBall(ball)
+   local p, d = swing(ball.position.x, ball.direction.x, 0 + ball.radius, SCREEN_WIDTH - ball.radius)
+   ball.position.x = p
+   ball.direction.x = d
+
+   local p, d = swing(ball.position.y, ball.direction.y, 0 + ball.radius, SCREEN_HEIGHT - ball.radius)
+   ball.position.y = p
+   ball.direction.y = d
+end
+
+function swing(position, direction, min, max)
+   if (position <= min) then
+      position = min
+      direction = 1
+   elseif (position >= max) then
+      position = max
+      direction = -1
+   end
+
+   local dt = love.timer.getDelta()
+   position = position + (direction * BALL_SPEED * dt)
+   return position, direction
+end