Since naminukas in its current form is not very suitable for outdoor usage I was brainstorming solutions for a while now. One of options considered was to utilize a skateboard. For testing I made the simplest skateboard I could image. Wheels of prototype skateboard can't even be steered. To simulate uphill and downhill track I made a simple ramp from 4 pieces of old shower screen glass. This glass is supper strong and I tested that it can even survive a hit by a hammer. Here is a result of my initial experiments:

As you can notice in the video robot can't even drive up to the very top of the ramp. Wheel starts slipping at some point. So before trying outdoors I need to upgrade tires. One of ideas I have is to try using inverted timing belt as a wide tire.