I'd like to get some feedback on a small project http://ethpledge.com I've been working on the last few days. This is a smart contract and website where Ethereum users can pledge to donate a certain amount to an address (ideally a charity of some sort), which gets sent only if others match that amount. Upon creating a pledge to donate a certain amount to some address, the user sends that Ether to the EthPledge smart contract, and if others donate to that pledge too up to that amount of Ether it all gets sent to the charity address. You can also pledge to donate several times what others do (eg. you could put up 10 Ether, and say that if others donate only 2 Ether it'll all get sent to the charity address).

It is fairly common for companies to do giving pledges like this ("we'll match anything employees donate to this charity") and having something like this on the Ethereum blockchain makes it 100% transparent and by going through a smart contract can guarantee someone holds up their end of the bargain. There is at least one major international charity with an Ethereum address for donations, Heifer International (https://www.heifer.org/what-you-can-do/give/digital-currency.html) and I've created the first pledge on the website to donate 0.1 Ether to them: see http://www.ethpledge.com/id/0 (look at it while connected to the mainnet).

Should you create a pledge and then cancel it, you'll get a refund of your pledge amount in line with how much others have donated - if you cancel the pledge when 10% of the donation target has been reached, for example, 10% of your pledge amount (along with the donations) will be sent to the charity address, and 90% of the pledge amount you put up will be returned to you.

The verified contract code is at https://etherscan.io/address/0x10ec03b714a2660581040c1a0329d88e381ca603 and I've also uploaded the code for the website/UI at https://github.com/wanshun123/EthPledge if that's of interest to anyone.

Feedback and criticism very much welcome.

[Crypto Sprites]

If you've played the popular Crypto Kitties game and own kitties, this will be of interest to you.

Crypto Sprites allows Crypto Kitty owners to potentially make further income from their CryptoKitties by selling their separate Crypto Sprites, managed only within our own smart contract. Sprites are all kinds of fun video game style characters. Every CryptoKitty for sale in the original CryptoKitties game has a corresponding Sprite in this game, and funds from Sprite sales go straight to whichever Ethereum account owns the corresponding CryptoKitty. The default price of a Sprite now is only 10% of the price of its corresponding CryptoKitty, which may easily increase later. The price of an unsold Sprite can also be adjusted by the owner of the CryptoKitty (CryptoKitty owners can also remove their Sprites from sale if they like - by default ALL CryptoKitties for sale also have a Sprite that can be brought here).

Note the default price Sprites only being 10% of the cost of their Kitties will probably increase later. Currently, you can buy Sprites of cheap kitties for well under $1 USD. The game takes a 3% cut of all Sprite sales, of which 1.5% goes to a charity (Heifer International). You can also feature sprites for 0.01 Ether.

See https://www.CryptoSprites.com to start trading Sprites. Like with Crypto Kitties, you'll need MetaMask and some Ether to play the game. You can also view the verified source code of the Crypto Sprites contract at https://etherscan.io/address/0xf3C8Ed6C721774C022c530E813a369dFe78a6E85

Any feedback/comments welcome.

We've developed a game that builds off Crypto Kitties which we've had audited and are confident there are no critical bugs in the Solidity code, and would like to offer a bounty of 2 Ether for anyone who can find any critical bug (not interested in a code critique - only if there are any fatal issues with the contract). The contract is at https://etherscan.io/address/0x5acd164ebaecba00345d756c29364e6a6b17d5a4#code and the website is cryptosprites.com (not yet properly announced anywhere). By "critical bug" we mean something that would allow a user to steal a sprite or completely break the game. Naturally will only reward to the first person to report a bug if there are multiple submissions

This bounty is also posted at bounty0x: https://blog.bounty0x.io/bounty0x-spotlight-article-cryptosprites-41dec3f149b1