Train with space for electronics and batteries in carriage.

This train engine has space inside for some electronics, a 10mm led can fit in the front, and a 16mm button on the smoke stack, there is room to slide an Arduino/Compatible Pro-Mini inside the cab and into the boiler area, and in my one I had just enough more room to squeeze a JQ6500-28 MP3 SD Card player module and a mini speaker in the cab. What you do with yours is your business, but mine when you hit the button it plays a random train sound effect or train-related kids song while changing r