Not-a-black-window Celer Testnet: 401 Users, 4 award-winning cApps, 4817 Off-chain Games Played…

5 min read

We are totally amazed by ETHSanFrancisco (hosted by ETHGlobal). If you missed this great event, we invite you to feel the vibrant Ethereum developer community through this impression video made by one of our awesome community members!

Going into ETHSF, we wholeheartedly invited everyone to experience, build and have fun! We did exactly those three things and we would like to share our experiences!

A “not-black-window” Testnet

In ETHSanfrancisco, we soft launched cWallet to get valuable initial user feedbacks. The role of cWallet is first to serve as a entry point, through which users can experience, first-hand, actual blockchain applications powered by Celer’s off-chain scaling testnet Centauri. It also serves as a reference implementation, so that wallet developers can easily integrate Celer Network and dApp developers can easily transform their on-chain dApp to “cApps” .

Try it out!

During the short 36 hours, we have a whopping 401 cWallet installs! Every single user has experienced our instant payment application cPay: we have 719 off-chain payments by test users. We closely observed how users used off-chain payments to pay each other to aggregate balances to get more chances for our Celer Carnival games. There are a lot of user experience lessons we learnt and we will share them with some future writeups!

In cWallet, we also preinstalled a super fun off-chain board game cGomoku. In this game, you can bet some testnet ETH with any player in the world or your friends. We will have a separate writeup about this game, but the key points here are that the “staking process” is done via off-chain conditional payment and the entire game is realized as off-chain smart contract.

For this fun game, 4817 games was played and more than 150,000 state updates were made in ETHSF! On average we have more than 10 games played per user! Given the private nature of this soft launch, we are super excited about this repeated usage frequency!

More importantly, each off-chain smart contract state update takes milliseconds to complete on Celer. If these state updates were done on-chain, it would take 625 hours or 26 days. While the aggregated state update latency on Celer Network is less than 50mins.

750X faster Ethereum smart contract transaction is achieved! 😎

Download now at

Initial user feedbacks strengthened our belief that this kind of latency reduction brought by Celer is the inflection point for blockchain mass adoption.

We will have a dedicated blog to discuss the ins and outs of cWallet soon. If you cannot wait, try it yourself! 😃Download cWallet now at

4 Teams using Celer SDK won 4 BIG Prizes! Conditional payment is the theme!

Tech talk and SDK tutorial

In ETHSF, we also released Celer Network SDK for the first time! We gave a tech talk on Celer Network’s technology and economic construct in general and also gave an in-depth tutorial of Celer Network SDK. We are super excited to see talented developers immediately jumping on developing some super cool stuff using Celer Network SDK! You can access our SDK for Android here, for iOS here and for web stack here.

We also hosted three awards for this ETHSF: cInnovate for the most innovative application idea using Celer; cBuilder for the most complete implementation using Celer; cUX for application improving the user and developer experience of Celer. Interestingly, we found out that the concept of conditional payment promoted by Celer Network is very well accepted! We would like to proudly announce the award winning teams here!

🎉cBuilder Award, ETHSF Runner-up: Air Prediction offchain prediction market

We built the first-ever off-chain prediction market with the help of Celer Network and Chainlink. In our off-chain prediction market, users can submit an event for prediction by providing an oracle contract address. Then all users can place orders to bet on the result with some ethers. These orders will form an off-chain order book. Once YES and NO orders (think about bids and asks in a stock market) match, the corresponding issuers will get noticed and establish a bidirectional conditional payment through Celer Network. Based on the result given by the oracle contract provided by Chainlink, Celer Network will resolve the condition and settle the payments instantly without touching any on-chain transactions. — Air Prediction Team

UI of Air Prediction

With the amazing launch of Augur, everyone has his/her eyes on the renaissance of prediction market. However, the user experience of Augur today is far from ideal: order books are on-chain and every order takes painfully long time to confirm. If the UX issue remains unsolved, we definitely won’t see mass adoption. In addition, this slowness makes market making close to impossible and results in a large market spread, shallow market depth with low market efficiency. Without an efficient market, we cannot possibly hope to achieve the collective intelligence vision promised by prediction market. Celer Network naturally helps on the prediction market case with the clear abstraction of conditional off-chain payment, where the “condition” in this case is an on-chain oracle. We are in active communication with the team implemented this and they are reaching out to Augur to see if it is possible to help Augur scale!

🎉cBuilder Award 2: Micro Subscription cloud service with SLA guarantee

I was inspired by SLA example in chainlink repo. I realized that currently, it is not very convenient and efficient to resolve SLA dispute. With blockchain, I can programmingly resolve the dispute. Another issue I identified in current cloud service is that most of cloud service is subscribed by month, but it is not fair price model for user with low utilization. I think it will be very helpful to enable micro payment for service they actually use. There are multiple micro payment solutions out there, but I found out only Celer is able to support conditional payment by querying on-chain information. With conditional payment, I can use service condition to trigger payment. — Micro Subscription Team

UI for Microsubscription

We originally planned for only one cBuilder award, but this application is too perfect to be not rewarded and the implementation is fully functional and complete. This again is integrating Chainlink and Celer together! With this service, users can subscribe to cloud service by minutes and still have guaranteed SLA because when users are paying for the service provider, the service provider is also paying the user with conditional payment. If Chainlink declares the service is down, the conditional payment evaluates to be true and immediately users will be compensated for the loss! What an amazing idea and well executed prototype!

🎉cInnovate Award: Slick gas price option market

We deployed Layer 2 solutions built by Celer Network to mitigate the gas fee. Leveraging Celer Network’s conditional payment feature, we simulate a futures contract (due to the limitation of infrastructure, we hereby simplify the process by simulating a linear contract instead of nonlinear derivative in this hackathon) with discrete trigger thresholds. In this case, we act as a market maker for the future, and will hedge the risk of these futures positions against counterparties (likely miners) in the decentralized marketplace we hope to build beyond the scope of this hackathon. — Slick Team

UI of Slick

The idea of this app is quite innovative. It’s basically a flight insurance for gas fees. So let’s say you gotta a huge transaction you want to push through Ethereum but the gas fee was too high in the day time, you kinda want to wait until gas fee become cheaper at night. Now, some “market maker” may step up and say that he will help you to send out this transaction when the gas fee is low and he is saying that he can do it with 2Gwei with 5Gwei fee to him instead of 50Gwei you are paying right now. So what do you do? You could of course trust him and give him the 2Gwei-gas-price transaction and use Celer to do the 5Gwei-gas-price payment. However, you can also request the “market maker” to send you a conditional payment of 50Gwei on the condition that he failed to deliver your transaction on-time. This is effectively forming a option market for gas fee! Now we have a new way of pricing gas!

🎉cUX Award: Celer Templates for Composite Smart Contract IDE

I aim to simplify crypto development. Celer was a great opportunity since it is using a familiar framework (Truffle) yet is different enough to confuse developers. It creates an empty Celer smart contract with the right callback functions and deployment script — Celer Template team

Every state channel has standard interfaces to implement. Sometimes, it might be the case that developer may miss some key interfaces to implement. Therefore, this IDE provides a super useful way to generate a standard set of interfaces for channelized application. cUX award it is!

Interested in building? Join cPilot program now to receive free courses and get notify with online developer meetups!

Celer Carnival is a blast! 😹

During the ETHSF, we hosted Celer Carnival on our booth, attracted more than 500+ developers came and had fun!

By spinning the colorful wheel, attendees won a variety of Celer swags such as fidget spinners, bottle openers, notebooks..etc. Also, the first 100 developers who downloaded the cWallet dApps won the limited edition C’nicorn T-shirt!

We have also hosted our first King of cGomoku Game! ⚫️ ⚪️

Folks competed with one another on the cGomoku off-chain and discussed the strategies on winning. Most importantly, they were amazed by the off-chain conditional payment and how the entire game was implemented by the off-chain smart contract. There were 4817 games played in total and on average we have more than 10 games played per user! 😆 😆 Meet Howy, our King of cGomoku after winning the 2-hour survival competition!!

All Hail King Howy! 👑

Alright, that’s it for now. It has been a blast for us and see you next time in ETHSingapore!

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