How to build a steerable remote-controlled vehicle with just 1 motor? In WeDo 2.0 set there is only 1 motor, which can be remotely switched on and off by using the iPad app (by writing a Scratch program). 

Also motor rotating direction can be toggled remotely.



As an inexperienced LEGO builder I wonder if it is possible to build a remote-controlled vehicle out of 280 WeDo 2.0 pieces, which would be steered by changing the motor rotation direction.



I am thinking of having 2 wheels with wide tires in front the vehicle, connected to the motor.

And having a single caster wheel with narrow tire at the back of the vehicle, not connected to the motor.

The caster wheel would roll straight, when the vehicle drives forwards.

But when driving backwards, it would snap to a certain angle.

UPDATE 3:

Found a picture for such a caster wheel in the LEGO Technic Idea Book by Mr. Yoshihito Isogawa:



UPDATE:

I have followed Aaganrmu's suggestion (thank you) and have tried to build a simple vehicle using ratchet instead of caster wheel:

https://www.youtube.com/watch?v=uqYQ79SdBpY

Unfortunately, it doesn't work well. There is too much friction - on the axles of all 3 wheels and on the rubber band.

I wonder if experienced LEGO builders can propose a better vehicle out of WeDo 2.0 parts than mine:











And I feel that my Scratch program can be improved too, since it is not very responsive to user input (when touching the 4 green arrows):



UPDATE 2: Got a nice suggestion at Eurobricks forum:



(video authored by Mr. Yoshihito Isogawa again).

UPDATE 4:

Here a good WeDo 2.0 model with steering:

https://www.youtube.com/watch?v=Q9sd4MxW4YY
This can be done without a caster wheel as well:

Start out with a three wheeled vehicle, with two wheels in the front and one smaller wheel with less traction than the front wheels in the back. All wheels need to be fixed.

One of the front wheels is attached to the motor. This might need to have some gearing to get an appropriate speed.
The other front wheel is unpowered but can only rotate forward by adding a ratchet:  



The back wheel is unpowered.

Driving forward the vehicle will more or less move straight, guided by the rear wheel.
Driving backwards the ratchet will engage, stopping one wheel. The vehicle will now turn.