Add shareware support and spawn correctly for difficulty levels

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/features/renderer/weapon_painter.dart

@@ -1,8 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:wolf_dart/classes/sprite.dart';
 import 'package:wolf_dart/features/renderer/color_palette.dart';
 
 class WeaponPainter extends CustomPainter {
-  final List<List<int>> sprite;
+  final Sprite? sprite;
 
   // Initialize a reusable Paint object and disable anti-aliasing to keep the
   // pixels perfectly sharp and chunky.
@@ -14,6 +15,8 @@ class WeaponPainter extends CustomPainter {
 
   @override
   void paint(Canvas canvas, Size size) {
+    if (sprite == null) return;
+
     // Calculate width and height separately in case the container isn't a
     // perfect square
     double pixelWidth = size.width / 64;
@@ -21,7 +24,7 @@ class WeaponPainter extends CustomPainter {
 
     for (int x = 0; x < 64; x++) {
       for (int y = 0; y < 64; y++) {
-        int colorByte = sprite[x][y];
+        int colorByte = sprite![x][y];
 
         if (colorByte != 255) {
           // 255 is our transparent magenta