qmk_firmware/keyboards/handwired/gamenum/gamenum.h

#ifndef GAMENUM_H
#define GAMENUM_H

#include "quantum.h"

#define KEYMAP( \
	k00, k01, k02, k03, \
	k10, k11, k12, k13, \
	k20, k21, k22,        \
	k30, k31, k32,        \
	       k41, k42, k43  \
) \
{ \
	{ k00, k01, k02, k03}, \
	{ k10, k11, k12, k13}, \
	{ k20, k21, k22, KC_NO}, \
	{ k30, k31, k32, KC_NO}, \
	{ KC_NO, k41, k42, k43}  \
}

#endif