qmk_firmware/quantum/led_matrix/animations/cycle_up_down_anim.h

#ifdef ENABLE_LED_MATRIX_CYCLE_UP_DOWN
LED_MATRIX_EFFECT(CYCLE_UP_DOWN)
#    ifdef LED_MATRIX_CUSTOM_EFFECT_IMPLS

static uint8_t CYCLE_UP_DOWN_math(uint8_t val, uint8_t i, uint8_t time) {
    return scale8(g_led_config.point[i].y - time, val);
}

bool CYCLE_UP_DOWN(effect_params_t* params) {
    return effect_runner_i(params, &CYCLE_UP_DOWN_math);
}

#    endif // LED_MATRIX_CUSTOM_EFFECT_IMPLS
#endif     // ENABLE_LED_MATRIX_CYCLE_UP_DOWN