I made one called Liyahu (main page at http://shenafu.com/smf/index.php?topic=94.0
and Omniglot page at http://www.omniglot.com/conscripts/liyahu.htm
The core concept is that of this trinity: mind, body, and soul. So the core symbols and meanings stem from these three concepts. From there, each concept can be expanded to encompass all sounds and meanings in the universe
. There are two parts: the 3 core glyphs and the 3 locations to place the glyphs. The main vowels associated with mind, body, and soul are respectively 'i', 'a', and 'u', when the glyphs are in their original locations. Other vowel sounds are created by moving the symbols to different locations. Consonants are formed with two glyphs in a single final graph, or letter.
Besides mind, body, and soul, other concepts can be derived. Regarding time, mind means future, body the present, and soul is tied to the past. The color of mind is blue, body is green, and soul is red. And so on for every thought, idea and thing. Words are formed by combining one or more graphs--letters--in a sequence that imparts the idea or thing. Take the name of the language, Liyahu. 'Li' stands for mind, because 'i' is the main sound of mind, and 'l' is the main consonant that consists of two mind glyphs. Same for 'ya' and 'hu' respectively to mean body and soul. Most words are made of two or three letters, such that the consonants and vowel convey the state, action, or changes as defined by the word. For instance, 'nga' means 'skeleton', where 'ng' consists of the body and soul glyphs. It means a physical structure that has an empty soul. The 'a' has just a body glyph and here it means the skeleton reinforces other physical objects or materials.
There is an official script, however, the concept is not limited to one writing system. Regardless of which writing system, they all have the same meanings and sounds. For example, at http://shenafu.com/smf/index.php?topic=94.msg433#msg433
, you can see alternative forms of writing and communications that follow the core concept of the trinity. Variant 1 is in semaphore form, suitable for use on flags et al. Variant 2 is shorthand for quick writing. I've tried it, and it's quite fun to write in. Variant 4 is more like cursive where the lines connect without lifting the pen from the paper. Variant 7 most resembles the original script, but also designed to be easy to write. Variant 11 is a linear script, such that all symbols connect across a center line.