\tikzmath{\t=-0.2;}
\tikzmath{\size=2;}

\coordinate (A) at (0,0);
\coordinate (B) at (0,\size);
\coordinate (C) at (\size,0);
\coordinate (D) at (\size,\size);
\coordinate (E) at (0.5*\size,0.5*\size);

\coordinate (T) at ($(A)!0.5!(C)$);
\coordinate (T) at ($(T)-(0,0.75)$);

\coordinate (Delta) at (1.75*\size,0);

\tikzstyle{A}=[anchor=south east]
\tikzstyle{B}=[anchor=north east]
\tikzstyle{C}=[anchor=south]
\tikzstyle{D}=[anchor=north]