  The main purpose of this paper is to describe the category of isotropic
cellular spectra over flexible fields. Guided by [9], we show that it is
equivalent as a stable $\infty$-category equipped with a $t$-structure to the
derived category of left comodules over the dual of the classical topological
Steenrod algebra. In order to obtain this result, the category of isotropic
cellular modules over the motivic Brown-Peterson spectrum is also studied and
isotropic Adams and Adams-Novikov spectral sequences are developed. As a
consequence, we also compute hom-sets in the category of isotropic Tate motives
between motives of isotropic cellular spectra.
