Add building preview

game/game_state.h

@@ -6,6 +6,14 @@
 
 #include "entity_map.h"
 
+typedef enum InputState {
+    INPUT_NONE,
+    INPUT_PLACING,
+    INPUT_DRAGGING,
+    INPUT_SELECTED_UNITS,
+    INPUT_SELECTED_OBJECT,
+} InputState;
+
 typedef struct Game {
     Camera2D camera;
     BzTileset terrainTileset;
@@ -14,10 +22,13 @@ typedef struct Game {
     BzTileMap map;
     EntityMap entityMap;
     f32 frameDuration;
-    Vector2 targetPos;
     ecs_entity_t entity;
     struct {
+        InputState state;
         int building;
+        bool buildingCanPlace;
+        TilePosition buildingPos;
+        TileSize buildingSize;
         Vector2 mouseDown;
         f32 mouseDownElapsed;
     } input;