Added difficulty screen

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

lib/classes/difficulty.dart

@@ -0,0 +1,12 @@
+enum Difficulty {
+  canIPlayDaddy(0, "Can I play, Daddy?"),
+  dontHurtMe(1, "Don't hurt me."),
+  bringEmOn(2, "Bring em' on!"),
+  iAmDeathIncarnate(3, "I am Death incarnate!"),
+  ;
+
+  final String title;
+  final int level;
+
+  const Difficulty(this.level, this.title);
+}

lib/classes/entity.dart

@@ -0,0 +1,19 @@
+enum EntityState { staticObj, idle, patrolling, shooting, pain, dead }
+
+class Entity {
+  double x;
+  double y;
+  int spriteIndex;
+  double angle;
+  EntityState state;
+  int mapId;
+
+  Entity({
+    required this.x,
+    required this.y,
+    required this.spriteIndex,
+    this.angle = 0.0,
+    this.state = EntityState.staticObj,
+    this.mapId = 0,
+  });
+}