How to make a shareware program with a free demo [

问题:

I have a game that I'd like to sell with the following system: give away a demo (say, with the first few levels) and sell the full version. I'd like to make the transition to the full version as seamless as possible for the user. I've never sold anything before online, so I'm not sure how that would work (even if there were no free demo).

This seems like a very common issue, so I'd imagine there's a standard solution. I'm writing in C++, targeting Windows, and my installer is generated by NSIS.

回答1:

There are two options:

1. A separate demo and full version. Your ecommerce provider will send the full version to people who buy it.
2. A demo that is unlocked by a registration key or online activation process. Registration keys can be generated on the fly (or taken from a pre-generated list). Ecommerce providers can then send the keys to customers immediately after purchase.

Both approaches have their pros and cons.

Separate full version

• Smaller demo file, saves bandwidth
• Less technical support required for customers who buy full version (in my experience)
• Two builds of the game, more testing
• Harder to distribute updated versions to customers - need to keep a login for each customer or a secret URL that expires after a few days.

Unlockable demo

• Contains all assets, may waste bandwidth
• Easier to distribute cracked version (pirates can distribute a 10KB patch or reg key and link to your demo file, more bandwidth waste)
• Single build, less testing
• Easy to distribute updated versions (everybody can download the same public version)

Regarding a "general" solution, look around for commercial DRM wrappers such as this one. Some game portals/publishers also require that you use their own wrapper.

回答2:

Don't ship your full product as a demo that can be activated. This way you don't eliminate piracy (which will still be something you will have to deal with) but at least you remove the possibility of someone just downloading the demo, cracking it, and spreading it around (or even just a cracked executable). They would at least have to buy the full version first.

As for checking a legit customer is using the software, you can indeed do some online authentication as Danny suggest but note that this will only stop people from using your online services and it often is just a matter of time before a qualified cracker/reverser makes sure that your product's offline features can be used without purchase.

By not shipping the full product immediately, it does make upgrading a little harder, but there are ways around this, ex: Updater that only works after online authentication.

回答3:

If you develop it correctly you should be able to have a checking mechanism after the Xth level. This checking mechanism could basically hit a registry key. This registry key could have some encoded information which was generated by your program. The key could basically represent an MD5 hash (or SHA-1 or SHA-2 if you really concerned with high security) of the installed machine MAC Address, the first and last name, so and so forth. When someone purchases the game, you have them input that data in a form and then generate a code to send along to the user to unlock the game. You could even take that same algorithm and put it on your ASP.NET website and automate the key generation after a purchase has been made.

回答4:

My 2 cents:

Dont spend too much time devising methods against piracy. Use simple serial generator mechanism to unlock the game which user can enter manually during the execution.

I would say have a single build which can switch to trial mode or full based on the serial key entered. This will reduce the overhead of maintaining two separate code.

It is a personal opinion, that people who really buy software at first place will buy your game no matter how many pirated versions are available. So make registeration purpose as simple as possible which will deter a normal user from cracking it and at the same time easy to use. Hackers will crack it no matter what protection you use it. Otherwise we wont see the pirated copies of microsoft/adobe products etc who spend so much on making their products piracy free. No matter what they charge, people do buy it. Its the quality of the product which will encourage your users to buy your product.

Also, try not to impose locks on your software like using MAC address etc for generating the serial numbers etc. Online activation may be a good idea but remember people are skeptical as to what information you try to transmit while activation. Also you might have to provide an alternate mechanism for offline activation if your customers dont have internet connection or work in separate LAN.

Once you see that you game is getting popular and you see more pirated copies with users, you may invest more time and money on developing anti-piracy techniques.