This document discusses smart contracts in the Σ-State language used by the Ergo Platform. It begins by describing some limitations of Bitcoin scripting and Ethereum's approach. The Σ-State language uses zero-knowledge proofs to enable more powerful cryptographic capabilities like ring and threshold signatures. Programs in the language combine these cryptographic statements with predicates over the transaction context in a simple logical formula. This approach allows for applications like crowdfunding, demurrage currencies, and more while ensuring verification time remains bounded.