Basic model where inflation occurs Why does inflation occur?  To an outsider, inflation appears somewhat mysterious.  Is there an extremely simple mathematical model where inflation naturally occurs?  I would like something that even someone with zero understanding of economics can appreciate.

UPDATE: I am hoping to find an agent-based model which is not defined in terms of inflation, but in terms of more basic (to me) things like supply, demand, et cetera, but where inflation occurs.  For example, the agents' goal could be to optimize revenue and they could have a limited set of possible actions.  Iterating their decisions could then lead to inflation.  Maybe such a model is nonsense, but I'd imagine that if it is not there would be papers about it.
Quoting Wikipedia:


  the quantity theory of money (QTM) states that money supply has a
  direct, proportional relationship with the price level.


According to this theory an increase in money in circulation increases price levels.

So an "extremely simple mathematical model" (and extremely simplistic) would be something like:

$$ \pi_t = \dfrac{M_t-M_{t-1}}{M_t} $$ where $M$ stands for money supply and $\pi$ stands for inflation.