Gem Glyph

The Gem Language is a language that appears in writing throughout Steven Universe in the background art, and as a minor plot point in "Monster Reunion". It is presumably one of the native languages of the Gem race.

The language is depicted in: An alternate form of the script appears throughout Attack the Light in scenery and in-game dialogue.
 * "Steven the Sword Fighter" (on the columns of Pearl's Arena),
 * "Sworn to the Sword", "Steven vs. Amethyst", and "Mindful Education" (on the columns of the Ancient Sky Arena),
 * "Monster Reunion" (on papers that Centipeetle writes on),
 * "Bismuth" (on one of the weapons in Forge),
 * "Gem Heist" (on the pillars of the Zoo's Containment Area),
 * "Lion 4: Alternate Ending" (on the walls of Rose's Landfill),
 * "Stuck Together" (on a notification in Aquamarine's Ship),
 * "Off Colors" and "Lars' Head" (on a destroyed pillar and in the Off Colors' headquarters, an abandoned Homeworld Kindergarten).

Main Script
Anything about the language's grammar, orthography, or lexicon in canon has yet to be revealed, and it has not been heard spoken. It is likely not an alternative script or substitution cipher for English, as it has more than 26 characters. Some of the characters resemble traditional (or simplified) Chinese; among those characters are: 中 (middle), 門 (door), 日 (day), 目 (eye), 几 (stool/amount), 月 (month), 山 (mountain), 开 (open), 王 (king), 田 (field), 丑 (ugly/clown), and 巳 (Sixth Earthly Branch\snake zodiac).

In "Monster Reunion", Centipeetle's script writes appears somewhat different to the previous instances of the script. The elements are written similarly to the Arabic script as opposed to the runes seen on the show. Steven mistakes these for meaningless scribbling when he first sees it, but Pearl describes it as "decently legible". It is possible this is a cursive or stylized form of the written language, or a different writing system entirely.

Alternate Script
The alternate script in the dialogue of Attack the Light uses the fonts Alien Lines Latin and Alien Sans Latin.

When directly translated from these fonts into readable text, "BLAH FHJOW NVG FKKD HFG" and "OUEIT JJOKLE" hold no meaning.

Trivia

 * Attack the Light's (and possibly non-canon) script also somewhat resembles the Pokémon "Unown", both resembling letters of the Roman alphabet made out of lines and circles.
 * Some characters vaguely resemble a TIE fighter and the Rebel Alliance symbol from Star Wars.