In our Trade-up Mechanism, each rarity has a failure rate called baseFailureRate and a failure time threshold called timeBase. Moreover, the failure rate will be determined by the total EXP of all Armoury NFTs which are selected to do trade-up, this EXP is referred to as collectiveEXP. The EXP of selected Armoury NFTs is inversely proportional to the failure rate, which means that the higher the total EXP of selected NFTs, the lower the failure rate. If all 4 NFT pieces don't have any experience point, the failure rate is equal to the base failure rate.