Suppose you are to write a recursive function to calculate the "area" of a triangle shown as follows, where the area of each $[]$ square is $1$:

$[][][][][][][][][]$

$[][][][][][][]$

$[][][][][]$

$[][][]$

$[]$

Assume the base of the triangle $($top edge$)$ always has an odd number of $[]$ squares, and each subsequent line has two fewer squares $($and hence the triangle always ends with a point that has just one $[]$ square$).$ What could be an appropriate base case for a recursive function that calculates the area of a triangle of this kind?