Thanks for the good critique and encouragement.
When I charted out the vowels, I did use the IPA chart as a guide. However, I had to convert it to a HTML table as neatly as possible. I guess I should draw up that IPA-like chart into an image file. As for the table, the vowels in rows 1 & 4 are front vowels, 2 & 5 are middle, and 3 & 6 are back. Every other column is unrounded and rounded, working from close to open.
Most of the vowels are drawn based on my personal feel of how I envision it. e.g. /ɐ/ I see it as a falling sound, thus a down-pointing arrow; /i/ is flat, no falling or rising; /e/ drops a bit from /i/; and /ɪ/ transitions from /i/ to /e/.
You may notice some of the symbols match up exactly to their IPA equivalents. It's partly coincidence, partly deliberate. While trying to find symbols that look different, I happened to like some of the IPA ones. And it so happens, their shapes match up with how I envision for that sound.
I understand your concern about what type of featural alphabet this is. My main concern was not trying to be too pedantic about articulation rules. For example, I don't want to end up with something like Visible Speech, where it's all about rules, and you think too much about rules before you can even understand the symbol. By the same token, I don't want something like Visible Speech and Tengwar where everything looks alike. Also, in Tengwar symbols don't give any guide to pronunciation. At least my symbols have simple general guidelines: you know which vowels are rounded or unrounded, you know if a tongue is involved and even how to curl the tongue, etc. So I settled for the best of both worlds--some hints to pronunciation, while having a good diversity and variation in the look of each symbol, and most importantly, being easy to read and write.
It should feel intuitive once you start writing and reading them. So not only the flow of reading, but the flow of writing should also feel smooth, quick, and intuitive.
, I figure it's very unlikely that a language would use both. So if you write it sloppily, there would be no difference within that language. And if you're on the computer, the difference would be noticeable enough. Anyhow, I can't think of an alternative for now.
You brought up tones like Cantonese. Actually, I was thinking up a syllablic design, not unlike Hangeul, but adding another dimension, namely tone. Suppose a syllabic grapheme is divided into 4 squares. Then, each square is occupied by an initial, a nucleus, a coda, and a tone marker, respectively. Of course, this only works with languages with simple, straightforward syllabic structure, like Cantonese. For Mandarin, it would be a bit harder because of medials /j/ and /w/. Now Cantonese does have some two-consonant combinations, noted as /t͡s/ and /kʷ/. For these, I created new symbols by merging the constituents so that they can fit into the grid where initials are placed.
For the tone marks, we can use the same ones as IPA: ˥ ˧˥ ˧ ˨˩ ˩˧ ˨ . Even though some of those symbols resemble other letters, there will be no confusion since one of the grids are reserved for tone marks. That is, only tone marks can go into that grid, and symbols in that grid mean tone, not phone.