Add missile trails

bundle/main.lua

@@ -7,6 +7,7 @@ local wall_thickness = 0.01
 
 local missiles = {}
 local missile_radius = 0.005
+local missile_trail_length = 7
 
 local window_width = nil
 local window_height = nil
@@ -57,28 +58,36 @@ function spawnMissile(x, y, dx, dy)
 		dx = dx,
 		dy = dy,
 		reflected = false,
+		history = {
+			{x = x, y = y}
+		}
 	})
 end
 
 function updateMissiles(dt)
-	for i, missile in ipairs(missiles) do
+	for _, missile in ipairs(missiles) do
 		missile.x = missile.x + missile.dx * dt
 		missile.y = missile.y + missile.dy * dt
 
+		local collided = false
+
 		if missile.y < wall_thickness + missile_radius then
 			-- Collision with top wall
 			missile.y = wall_thickness + missile_radius
 			missile.dy = -missile.dy
+			collided = true
 		end
 
 		if missile.x < wall_thickness + missile_radius then
 			-- Collision with left wall
 			missile.x = wall_thickness + missile_radius
 			missile.dx = -missile.dx
+			collided = true
 		elseif missile.x > 1 - (wall_thickness + missile_radius) then
 			-- Collision with right wall
 			missile.x = 1 - (wall_thickness + missile_radius)
 			missile.dx = -missile.dx
+			collided = true
 		end
 
 		local paddle_left = paddle_x - paddle_width/2
@@ -89,6 +98,18 @@ function updateMissiles(dt)
 			missile.y = paddle_top
 			missile.dy = -missile.dy
 			missile.reflected = true
+			collided = true
+		end
+
+		if collided then
+			table.insert(missile.history, 1, {
+				x = missile.x,
+				y = missile.y
+			})
+			-- Remove the oldest segments
+			if #missile.history > missile_trail_length then
+				table.remove(missile.history)
+			end
 		end
 	end
 
@@ -132,12 +153,32 @@ function drawWalls()
 end
 
 function drawMissiles()
+	love.graphics.setLineWidth(0.001 * scale)
+
+	-- Trails
+	for _, missile in ipairs(missiles) do
+		local from_x, from_y = toScreenCoordinates(missile.x, missile.y)
+		local visibility = 1
+		for _, point in ipairs(missile.history) do
+			local x, y = toScreenCoordinates(point.x, point.y)
+			if missile.reflected then
+				love.graphics.setColor(1 * visibility, 1 * visibility, 0.5 * visibility)
+			else
+				love.graphics.setColor(1 * visibility, 0.4 * visibility, 0 * visibility)
+			end
+			visibility = visibility * 0.8
+			love.graphics.line(from_x, from_y, x, y)
+			from_x = x
+			from_y = y
+		end
+	end
+
+	-- Missiles themselves. Drawn separately so that they're always over the trails
 	for _, missile in ipairs(missiles) do
 		local style = 'fill'
 		if missile.reflected then
 			love.graphics.setColor(1, 0.5, 0)
 			style = 'line'
-			love.graphics.setLineWidth(0.001 * scale)
 		else
 			love.graphics.setColor(1, 0.5, 0.5)
 		end