This simulation models the spatial spread of calcium over a 100 nm × 100 nm area for 2 seconds. Calcium entry begins at 500 ms and occurs in pulses from a central 30 nm‑diameter area containing 40 Calcium Channels similar to a cluster of Calcium Channels in a Calcium nanodomain. A calcium sensor marker is placed 30 nm from the center; mimicking a closely localised Ca2+ sensor such as Synaptotagmin. Play with the options below: for instance how does the Ca2+ buffer type affect activation of the Calicum sensor? What matters most, frequency or number of APs?