diff --git a/src/Prep/Prep.h b/src/Prep/Prep.h
index 14a0f88..d96616d 100644
--- a/src/Prep/Prep.h
+++ b/src/Prep/Prep.h
@@ -1,6 +1,49 @@
 #ifndef PREP_H
 #define PREP_H
 
+#include <cstdint>
+#include <ctime>
+#include <string>
+#include <vector>
+
+// For test example
 int add(int a, int b);
 
+// All IDs are uint32_t
+enum EventType { PHASE_CHANGE, ACTION, ROOM_STATE_CHANGE, PLAYER_STATE_CHANGE };
+enum Action { KILL, VOTE, INVESTIGATE, HEAL, PROTECT };
+enum RoomStatus { AWAITING_START, IN_PROGRESS, STOPPED, ENDED };
+enum PlayerStatus { KICKED, ALIVE, DEAD, VOTED_OUT };
+
+struct Role;
+struct Player;
+struct Room;
+struct Event;
+
+struct Role {
+    std::vector<Action> actions;
+};
+
+struct Player {
+    std::string username;
+    Role role;
+    PlayerStatus playerStatus;
+};
+
+struct Room {
+    std::string title;
+    std::tm *utcTimestampCreatedAt;
+    RoomStatus status;
+    uint32_t id;
+};
+
+struct Event {
+    std::string title;
+    std::tm *utcTimestampCreatedAt;
+    uint32_t numberNight;
+    bool isVisible;
+    std::vector<Action> causedBy;
+    std::vector<Action> influenced;
+};
+
 #endif