diff --git a/CMakeLists.txt b/CMakeLists.txt
index def597a..8f10524 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,12 +17,15 @@ include_directories(.)
 include_directories(${Boost_INCLUDE_DIR})
 
 add_executable(endgame-analyzer src/main.cpp src/state_explorer.cpp src/download.cpp
-        src/game_state.cpp
         include/null_buffer.h
         include/command_line_interface.h
         src/command_line_interface.cpp
         include/parse_game.h
         src/parse_game.cpp
+        include/hanabi_types.hpp
+        include/game_interface.h
+        src/hanabi_types.cpp
+        src/game_interface.cpp
 )
 
 target_link_libraries(endgame-analyzer cpr)
diff --git a/include/game_interface.h b/include/game_interface.h
new file mode 100644
index 0000000..9a2c884
--- /dev/null
+++ b/include/game_interface.h
@@ -0,0 +1,91 @@
+#ifndef DYNAMIC_PROGRAM_GAME_INTERFACE_H
+#define DYNAMIC_PROGRAM_GAME_INTERFACE_H
+
+#include <cstddef>
+#include <iosfwd>
+#include <vector>
+#include <unordered_map>
+#include <memory>
+#include "hanabi_types.hpp"
+
+
+namespace Hanabi
+{
+
+  struct CardMultiplicity
+  {
+    Card card;
+    unsigned multiplicity;
+
+    bool operator==(const CardMultiplicity &) const = default;
+  };
+
+  class HanabiStateIF {
+  public:
+    virtual void give_clue() = 0;
+    virtual void discard(hand_index_t index) = 0;
+    virtual void play(hand_index_t index) = 0;
+
+    virtual void rotate_next_draw(const Card& card) = 0;
+    virtual ActionType last_action_type() const = 0;
+    virtual void revert() = 0;
+
+    virtual void modify_clues(clue_t change) = 0;
+    virtual void set_clues(clue_t clues) = 0;
+
+    [[nodiscard]] virtual player_t turn() const = 0;
+    [[nodiscard]] virtual clue_t num_clues() const = 0;
+    [[nodiscard]] virtual unsigned score() const = 0;
+    [[nodiscard]] virtual std::vector<std::vector<Card>> hands() const = 0;
+    [[nodiscard]] virtual std::vector<Card> cur_hand() const = 0;
+    [[nodiscard]] virtual size_t draw_pile_size() const = 0;
+
+    [[nodiscard]] virtual bool is_trash(const Card& card) const = 0;
+    [[nodiscard]] virtual bool is_playable(const Card& card) const = 0;
+    [[nodiscard]] virtual bool is_relative_state_initialized() const = 0;
+    [[nodiscard]] virtual hand_index_t find_card_in_hand(const Card& card) const = 0;
+
+    [[nodiscard]] virtual std::uint64_t enumerated_states() const = 0;
+    [[nodiscard]] virtual const std::unordered_map<unsigned long, probability_t>& position_tablebase() const = 0;
+
+    virtual void init_backtracking_information() = 0;
+    virtual probability_t evaluate_state() = 0;
+
+    [[nodiscard]] virtual std::optional<probability_t> lookup() const = 0;
+    [[nodiscard]] virtual std::uint64_t unique_id() const = 0;
+    [[nodiscard]] virtual std::pair<std::vector<std::uint64_t>, std::vector<Card>> dump_unique_id_parts() const = 0;
+
+    virtual std::vector<std::pair<Action, std::optional<probability_t>>> get_reasonable_actions() = 0;
+    virtual std::vector<std::pair<CardMultiplicity, std::optional<probability_t>>> possible_next_states(hand_index_t index, bool play) = 0;
+
+    virtual ~HanabiStateIF() = default;
+
+  protected:
+    virtual void print(std::ostream& os) const = 0;
+
+    friend std::ostream& operator<<(std::ostream&, HanabiStateIF const&);
+  };
+
+  std::ostream &operator<<(std::ostream &os, HanabiStateIF const &hanabi_state);
+
+  struct Game {
+    Game(std::unique_ptr<HanabiStateIF> state, std::vector<Action> actions, std::vector<Card> deck);
+
+    [[nodiscard]] unsigned cur_turn() const;
+
+    void make_turn();
+    void revert_turn();
+
+    bool goto_draw_pile_size(size_t draw_pile_break);
+    bool goto_turn(size_t turn);
+
+    [[nodiscard]] bool holds_state() const;
+
+    std::unique_ptr<HanabiStateIF> state;
+    std::vector<Action> actions;
+    std::vector<Card> deck;
+    unsigned next_action;
+  };
+
+}
+#endif //DYNAMIC_PROGRAM_GAME_INTERFACE_H
diff --git a/include/game_state.h b/include/game_state.h
index b1acc26..575955f 100644
--- a/include/game_state.h
+++ b/include/game_state.h
@@ -16,135 +16,15 @@
 #include <boost/container/static_vector.hpp>
 #include <boost/rational.hpp>
 
+#include "game_interface.h"
 
 namespace Hanabi {
 
-    using rank_t = std::uint8_t;
-    using suit_t = std::uint8_t;
-    using clue_t = std::int8_t;
-    using player_t = std::uint8_t;
-    using hand_index_t = std::uint8_t;
-
-    using probability_base_type = unsigned long;
-    using rational_probability = boost::rational<probability_base_type>;
-
-/**
- * Define macro
- * NUSE_RATIONAL_PROBABILITIES
- * to use floating-point arithematic for the stored probabilities
- * instead of rational representations
-*/
-
-#ifndef NUSE_RATIONAL_PROBABILITIES
-    using probability_t = boost::rational<probability_base_type>;
-#else
-    using probability_t = double;
-#endif
-
-    inline std::ostream& print_probability(std::ostream& os, double prob);
-    inline std::ostream& print_probability(std::ostream& os, const rational_probability& prob);
-
-    template<typename T>
-    std::ostream& print_probability(std::ostream& os, const std::optional<T>& prob);
-
-    /**
-     * We will generally assume that stacks are played from n to 0
-     * Playing a 0 will yield a clue
-     * Therefore, for the default hanabi, we will play 4,3,2,1,0 in that order
-     * on each stack. A stack with no cards played implicitly has value 5 on it
-     * This is just easier to implement, since then the remaining number of cards
-     * to be played is always the current number of the stack
-     */
-    constexpr rank_t starting_card_rank = 5;
-    constexpr suit_t max_suit_index = 5;
-    constexpr size_t max_card_duplicity = 3;
-    constexpr clue_t max_num_clues = 8;
-    constexpr uint8_t not_in_starting_hand = std::numeric_limits<uint8_t>::max();
-    constexpr hand_index_t invalid_hand_idx = std::numeric_limits<hand_index_t>::max();
-
-    // We might want to change these at runtime to adapt to other variants.
-    // However, a global variable is used so that we can have an output operator for cards reading from here
-    // Note that this is therefore not static so that we have external linking
-    inline std::array<char, 6> suit_initials = {'r', 'y', 'g', 'b', 'p', 't'};
-
-    struct Card {
-        suit_t suit;
-        rank_t rank;
-        uint8_t local_index;
-        bool in_starting_hand;
-        bool initial_trash;
-
-        inline bool operator==(const Card &other) const;
-    };
-
-    namespace Cards {
-        static constexpr Card r0 = {0, 5};
-        static constexpr Card r1 = {0, 4};
-        static constexpr Card r2 = {0, 3};
-        static constexpr Card r3 = {0, 2};
-        static constexpr Card r4 = {0, 1};
-        static constexpr Card r5 = {0, 0};
-        static constexpr Card y0 = {1, 5};
-        static constexpr Card y1 = {1, 4};
-        static constexpr Card y2 = {1, 3};
-        static constexpr Card y3 = {1, 2};
-        static constexpr Card y4 = {1, 1};
-        static constexpr Card y5 = {1, 0};
-        static constexpr Card g0 = {2, 5};
-        static constexpr Card g1 = {2, 4};
-        static constexpr Card g2 = {2, 3};
-        static constexpr Card g3 = {2, 2};
-        static constexpr Card g4 = {2, 1};
-        static constexpr Card g5 = {2, 0};
-        static constexpr Card b0 = {3, 5};
-        static constexpr Card b1 = {3, 4};
-        static constexpr Card b2 = {3, 3};
-        static constexpr Card b3 = {3, 2};
-        static constexpr Card b4 = {3, 1};
-        static constexpr Card b5 = {3, 0};
-        static constexpr Card p0 = {4, 5};
-        static constexpr Card p1 = {4, 4};
-        static constexpr Card p2 = {4, 3};
-        static constexpr Card p3 = {4, 2};
-        static constexpr Card p4 = {4, 1};
-        static constexpr Card p5 = {4, 0};
-        static constexpr Card t0 = {5, 5};
-        static constexpr Card t1 = {5, 4};
-        static constexpr Card t2 = {5, 3};
-        static constexpr Card t3 = {5, 2};
-        static constexpr Card t4 = {5, 1};
-        static constexpr Card t5 = {5, 0};
-        static constexpr Card unknown = {std::numeric_limits<suit_t>::max(), 0};
-        static constexpr Card trash = {std::numeric_limits<suit_t>::max(), 1};
-    }
-}
-
-namespace Hanabi {
-
-inline std::string to_string(const Hanabi::Card &card);
-inline std::ostream &operator<<(std::ostream &os, const Card &card);
-
-
-/**
- * To store:
- * - Draw pile size
- * - Distribution of cards
- *      - Which cards exist?
- * - Number of clues
- */
-
-template <size_t num_suits>
+template<size_t num_suits>
 using Stacks = std::array<rank_t, num_suits>;
 
-template <size_t num_suits>
-std::ostream& operator<<(std::ostream &os, const Stacks<num_suits> &stacks);
-
-struct CardMultiplicity {
-  Card card;
-  unsigned multiplicity;
-
-  bool operator==(const CardMultiplicity &) const = default;
-};
+template<size_t num_suits>
+std::ostream &operator<<(std::ostream &os, const Stacks<num_suits> &stacks);
 
 template<typename T>
 struct InnerCardArray {
@@ -177,100 +57,9 @@ private:
     std::array<inner_array_t , num_suits> _array {};
 };
 
-enum class ActionType : std::uint8_t {
-    play = 0,
-    discard = 1,
-    clue = 2,
-    color_clue = 2,
-    rank_clue = 3,
-    end_game = 4,
-    vote_terminate_players = 5,
-    vote_terminate = 10,
-};
-
-struct Action {
-    ActionType type {};
-    Card card {};
-};
-
-inline std::ostream& operator<<(std::ostream& os, const Action& action);
-
-/** Would like to have 2 versions:
- * All:
- *  - support playing cards, querying basic information
- *  - support going back, but with a different interface: efficient (needs arguments, does not store) or using a stack
- *
- */
-
-class HanabiStateIF {
-public:
-    virtual void give_clue() = 0;
-    virtual void discard(hand_index_t index) = 0;
-    virtual void play(hand_index_t index) = 0;
-
-    virtual void rotate_next_draw(const Card& card) = 0;
-    virtual ActionType last_action_type() const = 0;
-    virtual void revert() = 0;
-
-    virtual void modify_clues(clue_t change) = 0;
-    virtual void set_clues(clue_t clues) = 0;
-
-    [[nodiscard]] virtual player_t turn() const = 0;
-    [[nodiscard]] virtual clue_t num_clues() const = 0;
-    [[nodiscard]] virtual unsigned score() const = 0;
-    [[nodiscard]] virtual std::vector<std::vector<Card>> hands() const = 0;
-    [[nodiscard]] virtual std::vector<Card> cur_hand() const = 0;
-    [[nodiscard]] virtual size_t draw_pile_size() const = 0;
-
-    [[nodiscard]] virtual bool is_trash(const Card& card) const = 0;
-    [[nodiscard]] virtual bool is_playable(const Card& card) const = 0;
-    [[nodiscard]] virtual bool is_relative_state_initialized() const = 0;
-    [[nodiscard]] virtual hand_index_t find_card_in_hand(const Card& card) const = 0;
-
-    [[nodiscard]] virtual std::uint64_t enumerated_states() const = 0;
-    [[nodiscard]] virtual const std::unordered_map<unsigned long, probability_t>& position_tablebase() const = 0;
-
-    virtual void init_backtracking_information() = 0;
-    virtual probability_t evaluate_state() = 0;
-
-    [[nodiscard]] virtual std::optional<probability_t> lookup() const = 0;
-    [[nodiscard]] virtual std::uint64_t unique_id() const = 0;
-    [[nodiscard]] virtual std::pair<std::vector<std::uint64_t>, std::vector<Card>> dump_unique_id_parts() const = 0;
-
-    virtual std::vector<std::pair<Action, std::optional<probability_t>>> get_reasonable_actions() = 0;
-    virtual std::vector<std::pair<CardMultiplicity, std::optional<probability_t>>> possible_next_states(hand_index_t index, bool play) = 0;
-
-    virtual ~HanabiStateIF() = default;
-
-protected:
-    virtual void print(std::ostream& os) const = 0;
-
-    friend std::ostream& operator<<(std::ostream&, HanabiStateIF const&);
-};
 
 // A game mimics a game state together with a list of actions and allows to traverse the game
 // history by making and reverting the stored actions.
-struct Game {
-  Game(std::unique_ptr<HanabiStateIF> state, std::vector<Action> actions, std::vector<Card> deck);
-
-  unsigned cur_turn() const;
-
-  void make_turn();
-  void revert_turn();
-
-  bool goto_draw_pile_size(size_t draw_pile_break);
-  bool goto_turn(size_t turn);
-
-  bool holds_state();
-
-  std::unique_ptr<HanabiStateIF> state;
-  std::vector<Action> actions;
-  std::vector<Card> deck;
-  unsigned next_action;
-};
-
-inline std::ostream &operator<<(std::ostream &os, HanabiStateIF const &hanabi_state);
-
 template <suit_t num_suits, player_t num_players, hand_index_t hand_size>
 class HanabiState : public HanabiStateIF {
 public:
diff --git a/include/game_state.hpp b/include/game_state.hpp
index 294b739..61bc49b 100644
--- a/include/game_state.hpp
+++ b/include/game_state.hpp
@@ -6,65 +6,6 @@
 
 namespace Hanabi {
 
-    template<typename T>
-    std::ostream& print_probability(std::ostream& os, const std::optional<T>& prob) {
-        if (prob.has_value()) {
-            return print_probability(os, prob.value());
-        } else {
-            os << "unknown";
-        }
-        return os;
-    }
-
-    std::ostream& print_probability(std::ostream& os, const rational_probability & prob) {
-        os << prob << " ~ " << std::setprecision(5) << boost::rational_cast<double>(prob) * 100 << "%";
-        return os;
-    }
-
-    std::ostream& print_probability(std::ostream& os, double prob) {
-        os << std::setprecision(5) << prob;
-        return os;
-    }
-
-    std::ostream &operator<<(std::ostream &os, HanabiStateIF const &hanabi_state) {
-        hanabi_state.print(os);
-        return os;
-    }
-
-    std::string to_string(const Hanabi::Card &card) {
-        if (card == Hanabi::Cards::trash) {
-            return "kt";
-        } else {
-            return Hanabi::suit_initials[card.suit] + std::to_string(5 - card.rank);
-        }
-    }
-
-    std::ostream &operator<<(std::ostream &os, Action const& action) {
-        switch(action.type) {
-            case ActionType::play:
-                os << "play " + to_string(action.card);
-                break;
-            case ActionType::discard:
-                os << "discard";
-                break;
-            case ActionType::clue:
-                os << "clue";
-                break;
-            default:
-                break;
-        }
-        return os;
-    }
-
-    bool Card::operator==(const Card &other) const {
-        return suit == other.suit and rank == other.rank;
-    }
-
-    std::ostream &operator<<(std::ostream &os, const Card &card) {
-        os << to_string(card);
-        return os;
-    }
-
     template<size_t num_suits>
     std::ostream &operator<<(std::ostream &os, const Stacks<num_suits> &stacks) {
         for (size_t i = 0; i < stacks.size(); i++) {
diff --git a/include/hanabi_types.hpp b/include/hanabi_types.hpp
new file mode 100644
index 0000000..2fa170e
--- /dev/null
+++ b/include/hanabi_types.hpp
@@ -0,0 +1,157 @@
+#ifndef DYNAMIC_PROGRAM_HANABI_TYPES_H
+#define DYNAMIC_PROGRAM_HANABI_TYPES_H
+
+#include <cstdint>
+#include <iosfwd>
+#include <array>
+#include <optional>
+
+#include <boost/rational.hpp>
+
+namespace Hanabi {
+
+  using rank_t = std::uint8_t;
+  using suit_t = std::uint8_t;
+  using clue_t = std::int8_t;
+  using player_t = std::uint8_t;
+  using hand_index_t = std::uint8_t;
+
+  using probability_base_type = unsigned long;
+  using rational_probability = boost::rational<probability_base_type>;
+
+/**
+ * Define macro
+ * NUSE_RATIONAL_PROBABILITIES
+ * to use floating-point arithematic for the stored probabilities
+ * instead of rational representations
+*/
+
+#ifndef NUSE_RATIONAL_PROBABILITIES
+  using probability_t = boost::rational<probability_base_type>;
+#else
+  using probability_t = double;
+#endif
+
+  std::ostream& print_probability(std::ostream& os, const rational_probability& prob);
+  std::ostream& print_probability(std::ostream& os, double prob);
+
+  template<typename T>
+  std::ostream& print_probability(std::ostream& os, const std::optional<T>& prob);
+
+  /**
+   * We will generally assume that stacks are played from n to 0
+   * Playing a 0 will yield a clue
+   * Therefore, for the default hanabi, we will play 4,3,2,1,0 in that order
+   * on each stack. A stack with no cards played implicitly has value 5 on it
+   * This is just easier to implement, since then the remaining number of cards
+   * to be played is always the current number of the stack
+   */
+  constexpr rank_t starting_card_rank = 5;
+  constexpr suit_t max_suit_index = 5;
+  constexpr size_t max_card_duplicity = 3;
+  constexpr clue_t max_num_clues = 8;
+  constexpr hand_index_t invalid_hand_idx = std::numeric_limits<hand_index_t>::max();
+
+  // We might want to change these at runtime to adapt to other variants.
+  // However, a global variable is used so that we can have an output operator for cards reading from here
+  // Note that this is therefore not static so that we have external linking
+  inline std::array<char, 6> suit_initials = {'r', 'y', 'g', 'b', 'p', 't'};
+
+  struct Card {
+    suit_t suit;
+    rank_t rank;
+
+    // These attributes are not needed in general for a card,
+    // they represent internal states during backtracking.
+    uint8_t local_index;
+    bool in_starting_hand;
+    bool initial_trash;
+
+    /**
+     * @brief Compares cards *only* regarding suit and rank.
+     * This is inlined as this is a runtime critical function when backtracking.
+     */
+    inline bool operator==(const Card &other) const;
+  };
+
+  enum class ActionType : std::uint8_t {
+    play = 0,
+    discard = 1,
+    clue = 2,
+    color_clue = 2,
+    rank_clue = 3,
+    end_game = 4,
+    vote_terminate_players = 5,
+    vote_terminate = 10,
+  };
+
+  struct Action {
+    ActionType type {};
+    Card card {};
+  };
+
+  // Output utilities for Cards and Actions
+  std::string to_string(const Card &card);
+  std::ostream &operator<<(std::ostream &os, const Card & card);
+  std::ostream& operator<<(std::ostream& os, const Action& action);
+
+
+  namespace Cards {
+    static constexpr Card r0 = {0, 5};
+    static constexpr Card r1 = {0, 4};
+    static constexpr Card r2 = {0, 3};
+    static constexpr Card r3 = {0, 2};
+    static constexpr Card r4 = {0, 1};
+    static constexpr Card r5 = {0, 0};
+    static constexpr Card y0 = {1, 5};
+    static constexpr Card y1 = {1, 4};
+    static constexpr Card y2 = {1, 3};
+    static constexpr Card y3 = {1, 2};
+    static constexpr Card y4 = {1, 1};
+    static constexpr Card y5 = {1, 0};
+    static constexpr Card g0 = {2, 5};
+    static constexpr Card g1 = {2, 4};
+    static constexpr Card g2 = {2, 3};
+    static constexpr Card g3 = {2, 2};
+    static constexpr Card g4 = {2, 1};
+    static constexpr Card g5 = {2, 0};
+    static constexpr Card b0 = {3, 5};
+    static constexpr Card b1 = {3, 4};
+    static constexpr Card b2 = {3, 3};
+    static constexpr Card b3 = {3, 2};
+    static constexpr Card b4 = {3, 1};
+    static constexpr Card b5 = {3, 0};
+    static constexpr Card p0 = {4, 5};
+    static constexpr Card p1 = {4, 4};
+    static constexpr Card p2 = {4, 3};
+    static constexpr Card p3 = {4, 2};
+    static constexpr Card p4 = {4, 1};
+    static constexpr Card p5 = {4, 0};
+    static constexpr Card t0 = {5, 5};
+    static constexpr Card t1 = {5, 4};
+    static constexpr Card t2 = {5, 3};
+    static constexpr Card t3 = {5, 2};
+    static constexpr Card t4 = {5, 1};
+    static constexpr Card t5 = {5, 0};
+    static constexpr Card unknown = {std::numeric_limits<suit_t>::max(), 0};
+    static constexpr Card trash = {std::numeric_limits<suit_t>::max(), 1};
+  }
+
+  //// INLINE SECTION
+
+  bool Card::operator==(const Card &other) const {
+    return suit == other.suit and rank == other.rank;
+  }
+
+  template<typename T>
+  std::ostream& print_probability(std::ostream& os, const std::optional<T>& prob) {
+    if (prob.has_value()) {
+      return print_probability(os, prob.value());
+    } else {
+      os << "unknown";
+    }
+    return os;
+  }
+
+} // namespace Hanabi
+#endif //DYNAMIC_PROGRAM_HANABI_TYPES_H
diff --git a/src/game_state.cpp b/src/game_interface.cpp
similarity index 88%
rename from src/game_state.cpp
rename to src/game_interface.cpp
index c026b5c..a83947d 100644
--- a/src/game_state.cpp
+++ b/src/game_interface.cpp
@@ -1,11 +1,16 @@
-#include <iostream>
-#include <utility>
-#include "game_state.h"
+#include "game_interface.h"
+#include "myassert.h"
 
 namespace Hanabi {
 
+  std::ostream &operator<<(std::ostream &os, HanabiStateIF const &hanabi_state)
+  {
+    hanabi_state.print(os);
+    return os;
+  }
+
   Game::Game(std::unique_ptr<HanabiStateIF> state, std::vector<Action> actions, std::vector<Card> deck):
-  state(std::move(state)), actions(std::move(actions)), deck(std::move(deck)), next_action(0)
+        state(std::move(state)), actions(std::move(actions)), deck(std::move(deck)), next_action(0)
   {
     // If there is a 'Null' action that only signals the game's end, we want to get rid of it now,
     // as this will mess with our moves.
@@ -77,7 +82,7 @@ namespace Hanabi {
     return next_action + 1 == turn;
   }
 
-  bool Game::holds_state()
+  bool Game::holds_state() const
   {
     return state != nullptr;
   }
@@ -92,6 +97,4 @@ namespace Hanabi {
     }
     return state->draw_pile_size() == draw_pile_break;
   }
-
-
-}
+}
\ No newline at end of file
diff --git a/src/hanabi_types.cpp b/src/hanabi_types.cpp
new file mode 100644
index 0000000..b82ef5d
--- /dev/null
+++ b/src/hanabi_types.cpp
@@ -0,0 +1,45 @@
+#include "hanabi_types.hpp"
+
+namespace Hanabi {
+  std::ostream &operator<<(std::ostream &os, Action const& action) {
+    switch(action.type) {
+      case ActionType::play:
+        os << "play " + to_string(action.card);
+        break;
+      case ActionType::discard:
+        os << "discard";
+        break;
+      case ActionType::clue:
+        os << "clue";
+        break;
+      default:
+        break;
+    }
+    return os;
+  }
+
+
+  std::string to_string(const Hanabi::Card &card) {
+    if (card == Hanabi::Cards::trash) {
+      return "kt";
+    } else {
+      return Hanabi::suit_initials[card.suit] + std::to_string(5 - card.rank);
+    }
+  }
+
+  std::ostream &operator<<(std::ostream &os, const Card &card) {
+    os << to_string(card);
+    return os;
+  }
+
+  std::ostream& print_probability(std::ostream& os, const rational_probability & prob) {
+    os << prob << " ~ " << std::setprecision(5) << boost::rational_cast<double>(prob) * 100 << "%";
+    return os;
+  }
+
+  std::ostream& print_probability(std::ostream& os, double prob) {
+    os << std::setprecision(5) << prob;
+    return os;
+  }
+
+} // namespace Hanabi