Update 1.9

Previews
Prior to the release of Update 1.8, Topala said in a conversation at Touch Arcade Forums:

"I have a lot of ideas for update 1.9 that could be huge for the game, but more on that after I release 1.8... muahaha"

On August 13, 2014, Topala posted his first Update 1.9 preview image, which shows five icons wearing different-colored headphones. This made way for much anticipation throughout the Geometry Dash community, resulting in theories involving soundtrack changes within a level and new game modes.

On August 26, 2014, Topala created another image depicting three-dimensional blocks, arousing much excitement among Geometry Dash players. He continued with the idea on August 28, posting a picture on Facebook about what could be built using the blocks.

On September 6, 2014, another image was posted through Topala's social media accounts featuring several different new map components that would be used in future levels of Geometry Dash. This included two new icons, gear-like obstacles, and various different unknown types of blocks. The most prominent feature was a new thick blue portal that would likely result in another game mode being introduced. It was also released to the public that Topala would release the game to Steam, a popular internet-based social media platform.

On September 14, 2014, Topala posted yet another image onto his social media accounts. It has a blast and processor for Blast Processing by Waterflame and a book, an infinity symbol, and a "2" for Theory of Everything 2 by DJ Nate, with the latter likely to be the demon level, following similar lines to Update 1.6.

On September 21, 2014, another image was posted through Facebook and Twitter. This image introduced a new custom music feature that would allow players to include music from Newgrounds in their custom levels. The image includes ten icons with headphones at the bottom. It was the first picture to indicate that the update was a work in progress. Upon the release of the image, Topala said that a sneak peek video for the next levels would be coming soon.

On September 28, 2014, Topala officially released the first Update 1.9 sneak peek video, which showed the first 21 seconds of Blast Processing. As seen in the video, the new blue portal changed the icon to an arrow-like object with physics similar to those seen in the mobile game Wave Wave.

On October 10, 2014, he released another sneak peek video featuring the second level, Theory of Everything 2. In this video, a new background and a new design of ship was used. Topala was also playing the game on his computer, indicating that he may have been using the future Steam version.

On October 18, 2014, Topala confirmed that the update would be released soon after he had fixed a minor issues in the backup and music systems. He also said he was working on the Steam version, and hinted on Update 2.0, stating that he will continue improving the user account system devised in 1.9.

On November 4, 2014, Topala posted that the update was submitted for review and was waiting to be accepted.

On November 9, 2014, almost three months after Update 1.9 was first mentioned, Topala confirmed the release of 1.9 and stated that it would release to iOS and Android devices around the same time, and the Steam version would be released as soon as possible.

On November 13, 2014, Update 1.9 was released to the Windows Phone App Store.

On November 14, 2014, Update 1.91 was released to all devices. This was a minor update that fixed a few bugs.

On November 15, 2014 update 1.9 was released on Amazon devices.

On January 18, 2015 update 1.92 was released on Google Play. This included some new options and fixed few Custom Song bugs.

Introductions

 * New level "Blast Processing"
 * New level "Theory of Everything 2"
 * New "Wave" Game mode
 * New music system. Build and share levels using custom music from Newgrounds
 * Backup system! Store and sync your progress between devices and platforms
 * User account system. (Unique user names and backup, will include more in update 2.0)
 * New achievements, colors and icons.
 * Lots of new details and level objects.
 * Everyplay support for Android.
 * Customize the color of objects in the level editor (including 4 custom color channels).
 * Color coding in editor to make different objects more clear.
 * New search options.
 * Improved server performance for downloading levels.
 * Copy/paste support in editor. (not duplicate, paste object anywhere in the level).
 * Level editor object limit increased from 12,000 to 15,000
 * Lots of bug fixes and improvements.
 * The 99% achievement got nerfed to dying between 95% and 99%, making it possible to get the achievement in all main levels (including Lite ones), not just Electrodynamix.
 * A lot of difficulties for levels have been changed: Back on Track now is Easy, Polargeist and Dry Out now are Normal, Base After Base and Can't Let Go now are Hard and Jumper, Time Machine and Cycles are now Harder.
 * A new sound engine was introduced.
 * Stereo Madness' third coin was nerfed.
 * The game now automatically names your level "Unnamed 0" when you don't set a name for it. Your second unnamed level will be named "Unnamed 1", your third unnamed level will be named "Unnamed 2", and so forth.
 * A new secret achievement was added (Master Detective!)

As For Update 1.92:

 * New option that can help reduce lag on some devices ("options/smooth fix") & Other few new Settings options.
 * Added group features to level editor (Ability to separate Objects with Groups)
 * Max objects increased to 20,000.
 * Custom song bugfixes.
 * Steam users can now use their exclusive icons in the mobile version.
 * Random bugfixes and tweaks.

Trivia

 * The new arrow-like form, known as the Wave, was inspired by the mechanics of the mobile game Wave Wave. It is supposed the concept was brought to light by a popular Geometry Dash player, Darnoc, who created a level (also named Wave Wave), mimicking its mechanics using condensed groups of gravity rings and the UFO.
 * This is the first update to include a sequel of a main level song: Theory of Everything 2
 * This is the second update that includes two new main levels. (1.6 with Electroman Adventures and Clubstep, and now 1.9 with Blast Processing and Theory of Everything 2)
 * Both Update 1.6 and Update 1.9 featured music from both Waterflame and DJ Nate.
 * Some people thought that Eternity would be Level 18, but that was later proven false when the Theory of Everything 2 preview came out.
 * Many users thought that Update 1.9 would be released on Halloween, but the update ended up being released 9 days later.

Links

 * https://www.youtube.com/user/RobTopGames (YouTube Channel)
 * https://www.facebook.com/geometrydash (Facebook Account)
 * https://twitter.com/RobTopGames (Twitter Account)
 * http://forums.toucharcade.com/showthread.php?t=203823 (Touch Arcade Forums)