  $\omega$-regular energy games, which are weighted two-player turn-based games
with the quantitative objective to keep the energy levels non-negative, have
been used in the context of verification and synthesis. The logic of modal
$\mu$-calculus, when applied over game graphs with $\omega$-regular winning
conditions, allows defining symbolic algorithms in the form of fixed-point
formulas for computing the sets of winning states.
  In this paper, we introduce energy $\mu$-calculus, a multi-valued extension
of the $\mu$-calculus that serves as a symbolic framework for solving
$\omega$-regular energy games. Energy $\mu$-calculus enables the seamless reuse
of existing, well-known symbolic $\mu$-calculus algorithms for $\omega$-regular
games, to solve their corresponding energy augmented variants. We define the
syntax and semantics of energy $\mu$-calculus over symbolic representations of
the game graphs, and show how to use it to solve the decision and the minimum
credit problems for $\omega$-regular energy games, for both bounded and
unbounded energy level accumulations.
