Otto wheels didn't stop
The function to move forward or backward didn't stop after the delay. For a symple program like that: The Otto wheels need to move forward by 1 second than stop by 1 second.
void loop() { motorControl (-45, -45, 1 ); delay(1*1000); }
In this exemple, Otto will run forever. Ther is no intuitive way to stop the Otto.
Maybe to change this situation, We can change the motorControl function.
Actual: void motorControl(int rightSpeed, int leftSpeed, int stepDelay) { rightServo.write(90 + rightSpeed); leftServo.write(90 - leftSpeed); delay(stepDelay*1000);}
Proposition: void motorControl(int rightSpeed, int leftSpeed, int stepDelay) { rightServo.write(90 + rightSpeed); leftServo.write(90 - leftSpeed); delay(stepDelay*1000);rightServo.write(90);leftServo.write(90);}

Good point @lsprandel we will update that in the next release
Thanks! let us know if you find more improvements
Fixed in https://github.com/OttoDIY/blockly/commit/03860be0e943fb8cb3b3399f83ff19866b9a86ab