Each program has a Graphical User Interface (GUI) with menus
and submenus in the interface. To create excitations anywhere
in the tissue in __2D applications__,
use the mouse/touchpad **Click/Drag**, whereas in __3D applications__,
use **Ctrl+click/drag** with **PCs** and
**Command+click/drag** with **Mac OS**.
In the lattice-Boltzmann simulations, mouse clicks can be used to
add or remove obstacles based on the clicker type that can be chosen from
the simulation menu.

The main menus in the GUI are as follows.

- Simulation: press Solve/Pause to start or stop a simulation or Initialize to reinitialize the problem. Change the click radius and more.
- Model parameters: change interactively at any time. For example, it is possible to block or enhance currents or time constants. Some programs have predefined sets of parameters that can be chosen from a drop-down menu.
- Solver parameters: time integration variables, domain size and resolution.
- Display parameters: change the frame rate throttle to slow down or speed up the simulation according to graphics card or visualization speed needs. Colormaps and signal probe location visibility can also be changed, tip-trajectory options can be set through a sub-menu, and many more.
- Save Canvas: save a visualization result as a png image.
- Interval caller: make interactive calls to functions; for example, type in env.savePlot2D() in the 3-Variable Minimal Model to save the canvas automatically at a set interval.
- More complex models have many more menus and options. For example, the OVVR model has extensive menus to change the current multipliers, time coefficients, and cell types; record signals; display various currents; save and load parameters, etc.

- 3 Variable Minimal Model. See Reference (23).
- 3 Variable Rabbit Model with CytoD and DAM Drug Effects. See Supplementary Materials.
- 3 Variable Pig Model. See Supplementary Materials.
- 4 Variable Minimal Master Model. See References (16, 23, 45) and fit to other experiments.
- Beeler-Reuter Model. See Reference (49). This model has eight state variables.
- TP Model. See Reference (17). This model has 19 state variables.
- OVVR Model. See Reference (18). This model has originally 41 state variables. By using the TP sodium current in place of the original, the number of state variables in this version is 35.

- 3-Variable Minimal Model in a 8cm Cube using 128 grid points in each direction. See Reference (23) for model details.
- 3-Variable Minimal Model in a 16cm Cube using 256 grid points in each direction. This model may appear slow on older hardware as the numerical grid has over 16 million points! See Reference (23) for model details.
- CytoD (VF) and DAM (VT) Drug Effects in Rabbit. See Supplementary Materials.
- Beeler-Reuter Model in a Rabbit Structure. See Reference (49).
- Atrial Minimal Model. See Reference (45).
- Beeler-Reuter Model in an Atrial Structure. See Reference (49).
- Minimal Model in Porcine Ventricles See Supplementary Materials.
- TP Model in Porcine Ventricles. See Reference (17).
- OVVR Model in Porcine Ventricles. See Reference (18).

- Lattice-Boltzmann model of external fluid flow. See Reference (46).
- Lattice Boltzmann model of crystall growth in the presence of fluid flow. See Reference (48).