Raindrop Works has it's own Minecraft server for friends of the owner to join together on.  The server is a modded version of 1.12.2.  It is highly recommended that you use MultiMC for installation, and a guide is available on this page.  Look forward to joining you!
Image from Minecraft
Installation Guide
This guide presumes you haven't installed anything related to Minecraft on your computer.  As such, you may be able to get away with skipping some steps.

  1. Download MultiMC from the website on the sidebar and extract to a convenient location.  It's a standalone program so it doesn't have to be installed.
  2. Most users of Minecraft should already have the proper version of Java.  If you don't, use the link on the sidebar to get the most current version of Java 8.  Make sure to get the 64-bit version.  This modpack is fairly beefy, and I don't expect it to be able to run in the 4 GB memory limits that 32-bit Java apps have.
  3. Start MultiMC and go through the Quick Setup.  For most users the default settings should suffice.
  4. Now we need to add your user information to MultiMC so you can log in.  In the top right corner of the screen, click the "Profiles" drop down and select "Manage Accounts".
  5. Click "Add" and then fill in your account information.
  6. After that's done you can close the window and your account is linked.  The top corner of the main window should now show your display name.
  7. Since the launcher is configured, it's time to set up the game.  Select "Add Instance" from the top left corner.  This brings up the window for making a new game.  Chose "Import from ZIP" on the left toolbar.
  8. Either download the modpack from the sidebar or just right click and copy the address and use it to add the modpack to MultiMC.  Feel free to use a special icon or name in the top of the window, but it's not required.
  9. Click "OK".  MultiMC will work for a few moments setting up the basic settings.  If everything went right, you should now have a new icon for your game.  Double clicking will load the ServerSync software, and clicking the Sync button will start downloading the mod files.  The first time will take several minutes to download (It's pulling almost 500 MB of files from my server) but subsequent loads should be much faster as only changed mods need to be updated.
  10. When the sync is done, simply close that window and let the game load.  After the game is loaded, select "Multiplayer" and the server should already be pre-loaded and ready for you!
Older Versions
Those who have been around for a while may remember the old "Puddle Zone" minecraft worlds.  Fear not, they have not been forgotten.  They're just not running anymore.  The worlds will be uploaded through a cloud service for people who want to play on them to download and explore themselves.  Due to the movement of servers, the files aren't available at the moment, but that will be changing soon.
Important Links
Minecraft Modpack
Current Version 2.2 (updated 26 Oct 2019)
Uses Forge
Available from MultiMC's website here
Recommended version - Java 8 Update 231, available from here (make sure you get the 64 bit version)
Image from Minecraft