  We present Tempest, a synthesis tool to automatically create
correct-by-construction reactive systems and shields from qualitative or
quantitative specifications in probabilistic environments. A shield is a
special type of reactive system used for run-time enforcement; i.e., a shield
enforces a given qualitative or quantitative specification of a running system
while interfering with its operation as little as possible. Shields that
enforce a qualitative or quantitative specification are called safety-shields
or optimal-shields, respectively. Safety-shields can be implemented as
pre-shields or as post-shields, optimal-shields are implemented as
post-shields. Pre-shields are placed before the system and restrict the choices
of the system. Post-shields are implemented after the system and are able to
overwrite the system's output. Tempest is based on the probabilistic model
checker Storm, adding model checking algorithms for stochastic games with
safety and mean-payoff objectives. To the best of our knowledge, Tempest is the
only synthesis tool able to solve 2-1/2-player games with mean-payoff
objectives without restrictions on the state space. Furthermore, Tempest adds
the functionality to synthesize safe and optimal strategies that implement
reactive systems and shields
