fixed up exercise 23 (tween cancel)

main.lua

@@ -1,7 +1,7 @@
 -- debug --
-if os.getenv("LOCAL_LUA_DEBUGGER_VSCODE") == "1" then
+-- if os.getenv("LOCAL_LUA_DEBUGGER_VSCODE") == "1" then
-    require("lldebugger").start()
+--     require("lldebugger").start()
-end
+-- end
 
 -- libraries --
 Object = require 'lib/classic/classic'

obj/Healthbar.lua

@@ -10,14 +10,18 @@ function Healthbar:new(x, y, hp)
 end
 
 function Healthbar:decrease(amount)
-    if self.hp - amount <= 0 then
+    if self.hp ~= 0 then
-        self.hp = 0
+        if fg then timer:cancel(fg) end
-    else
+        if bg then timer:cancel(bg) end
-        self.hp = self.hp - amount
+        if self.hp - amount <= 0 then
+            self.hp = 0
+        else
+            self.hp = self.hp - amount
+        end
+        local target_width = self.max_width * (self.hp / 100)
+        fg = timer:tween(0.3, self, {qwidth = target_width}, 'in-out-cubic')
+        bg = timer:tween(0.6, self, {lwidth = target_width}, 'in-out-cubic')
     end
-    local target_width = self.max_width * (self.hp / 100)
-    timer:tween(0.3, self, {qwidth = target_width}, 'in-out-cubic')
-    timer:tween(0.6, self, {lwidth = target_width}, 'in-out-cubic')
 end
 
 function Healthbar:update(dt)