Thoughts as a computer engineer:

1. The motor demo didn't work for me (Firefox on Android). Nice to say it was made by Claude.

2. Voltage isn't like gravity. It's literally called potential. Voltage is the water being high up on the mountain. Gravity is the gravity, which was kinda the point of the analogy, no?

3. A Tesla has thousands not hundreds of 18650s. But I guess that's a superset.

4. For motor speed, I would use P = I x V. It shows the way the two work better, and the resulting P = I^2 x R = V^2 / R. Resistance is constant.

5. PWM wasn't explained right here. You can most certainly vary the voltage without PWM, and it's not just any old modulation you want. You want a binary output so your transistors don't go linear, and you can control the average power. PWM is easy for linear scaling. But you could presumably use other modulations.

6. It's important to understand what the H bridge is doing, why it matters, and what it offers. Shoot through and dead time are important. Understanding that the microcontroller outputs X current at Y voltage, and the motor needs J current at K voltage. You could drive a small enough motor directly.

7. Could maybe do a 2-cell charger with balance leads as a usability upgrade.

8. The 2 cells in series is upwards of 8.4v which is higher than the 5.5v that USB related chips allow and 6v that their absolute max is. Would be good to understand what the power chain is to make sure nothing blows up.

I think this is a good start and always kudos to those who learn, even more to this trying to teach others. Hopefully there's a part 2 going into more very simple theory. Especially a comparison vs the L298N.