Test passes now, and most of the gear is working, but now I think I can't use doctest because it doesn't support TAP output.

tests/game_engine.cpp

@@ -3,7 +3,7 @@
 
 TEST_CASE("game engine can start and take hit") {
   // test fails on purpose right now
-  GameEngine game{100};
+  GameEngine game{4};
   string err{"error"};
   game.hit(err);
   CHECK(game.is_dead() == true);