diff --git a/Makefile b/Makefile
index 7fb5ea8..80bef68 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ LIBS=clib-6502.a
 # Common source files
 ASM_SRCS = tk2k_startup.s
 C_SRCS = main.c monitor_subroutines.c utility.c \
-		game_graphics.c
+		game_graphics.c game_logic.c
 
 # Object files
 OBJS = $(ASM_SRCS:%.s=%.o) $(C_SRCS:%.c=%.o)
diff --git a/src/game_logic.c b/src/game_logic.c
new file mode 100644
index 0000000..8bf9235
--- /dev/null
+++ b/src/game_logic.c
@@ -0,0 +1,29 @@
+#include "game_logic.h"
+
+static uint8_t game_grid_alpha[GRID_WIDTH * GRID_HEIGHT];
+static uint8_t game_grid_beta[GRID_WIDTH * GRID_HEIGHT];
+
+static uint8_t *front_grid = game_grid_alpha;
+static uint8_t *back_grid = game_grid_beta;
+
+void swap_grids(void);
+
+void swap_grids(void) {
+	uint8_t *temp = front_grid;
+	
+	front_grid = back_grid;
+	back_grid = temp;
+}
+
+uint8_t *get_current_grid(void) {
+	return front_grid;
+}
+
+uint8_t *step_game(step_direction dir) {
+	// TODO: Update the grid state calculating the new state in the back grid
+	
+	
+	swap_grids();
+	
+	return front_grid;
+}
diff --git a/src/game_logic.h b/src/game_logic.h
new file mode 100644
index 0000000..94057cb
--- /dev/null
+++ b/src/game_logic.h
@@ -0,0 +1,19 @@
+#ifndef _GAME_LOGIC_HEADER_
+#define _GAME_LOGIC_HEADER_
+
+#include <stdint.h>
+
+#define GRID_WIDTH 5
+#define GRID_HEIGHT 5
+
+typedef enum {
+	UP,
+	DOWN,
+	LEFT,
+	RIGHT
+} step_direction;
+
+uint8_t *get_current_grid(void);
+uint8_t *step_game(step_direction dir);
+
+#endif /* _GAME_LOGIC_HEADER_ */