store selected shape id in game data

src/game/game.h

@@ -3,16 +3,25 @@
 #include <stdint.h>
 
 #include "../window/colour.h"
+#include "tetromino/shapes.h"
 
 // stores the data used in the game
 #define COLUMNS ((uint8_t)16)
 #define ROWS    ((uint8_t)(COLUMNS * 2))
 
+typedef struct {
+    ShapeId id;
+    uint8_t x;
+    uint8_t y;
+} SelectedShape;
+
 typedef struct {
     Colour columns[COLUMNS];
 } Row;
 
+
 typedef struct {
+    SelectedShape selected;
     Row row[ROWS];
 } GameData;