Leo Liu

It is so dark here. Did you bring a flashlight?
Yes. Here it is:
$$\begin{aligned}
\nabla \cdot \mathbf E &= \frac \rho {\epsilon_0}\\
\nabla \cdot\mathbf B &= 0\\
\nabla \times \mathbf E &= -\frac{\partial \mathbf B}{\partial t}\\
\nabla \times \mathbf B &= \mu_0 \left( \mathbf J + \epsilon_0 \frac{\partial \mathbf E}{\partial t} \right)\end{aligned}$$

$$\frac{\partial L}{\partial q}-\frac{d}{dt} \frac{\partial L}{\partial \dot q}=0$$
When nature gets lazy...