Hello, for this toy I used:
-a box of 15 by 8 cm.
-one dc motor with built-reducing, recycling an old telephone switchboard.
-one driver l293d motor, H-bridge
-a toggle switch and a push for detecting the position.
-as control device I used a atmega 328 Arduino programmable board, I hope to exchange it for a smaller microcontroller.
-as feeding, I recycled the switching power charger phone, provides 5V, 120mA, more than enough.

show a small operating video