add code so that enemy gains a new projectile when attacking falling enemies, and also draw the falling enemies

fcore/enemy/falling-enemies.sml

@@ -58,4 +58,56 @@ struct
            * as it is off screen *)
           updateList (pos - 1, vec, acc)
       end
+
+  fun helpGetDrawVec
+    (pos, fallingVec, width, height, ratio, xOffset, yOffset, acc) =
+    if pos = Vector.length fallingVec then
+      Vector.concat acc
+    else
+      let
+        val {x, y, variant = _, jumped = _} = Vector.sub (fallingVec, pos)
+
+        val x = Real32.fromInt x * ratio + xOffset
+        val y = Real32.fromInt y * ratio + yOffset
+        val size = Real32.fromInt Constants.enemySize * ratio
+
+        val vec = Block.lerp (x, y, size, size, width, height, 0.3, 0.3, 0.3)
+        val acc = vec :: acc
+      in
+        helpGetDrawVec
+          (pos + 1, fallingVec, width, height, ratio, xOffset, yOffset, acc)
+      end
+
+  fun getDrawVec (game: game_type, width, height) =
+    if Vector.length (#fallingEnemies game) = 0 then
+      Vector.fromList []
+    else
+      let
+        val fallingEnemies = #fallingEnemies game
+        val wratio = width / Constants.worldWidthReal
+        val hratio = height / Constants.worldHeightReal
+      in
+        if wratio < hratio then
+          let
+            val scale = Constants.worldHeightReal * wratio
+            val yOffset =
+              if height > scale then (height - scale) / 2.0
+              else if height < scale then (scale - height) / 2.0
+              else 0.0
+          in
+            helpGetDrawVec
+              (0, fallingEnemies, width, height, wratio, 0.0, yOffset, [])
+          end
+        else
+          let
+            val scale = Constants.worldWidthReal * hratio
+            val xOffset =
+              if width > scale then (width - scale) / 2.0
+              else if width < scale then (scale - width) / 2.0
+              else 0.0
+          in
+            helpGetDrawVec
+              (0, fallingEnemies, width, height, hratio, xOffset, 0.0, [])
+          end
+      end
 end