Okay, I've completed the Cathedral of Chaos, and it's indeed very good, with a few very interesting challenges (like the warped space-time part, and I just love the invisible walls/rotating fields part, gotta love these red shots), it's a visual experience (well, you don't get magnificient stuff like the waterfall and gate afterwards, but it's always interesting to visit), for instance I liked the monstruosity that's the boss Cheleball had problems with (though I did beat it using only the pellets, by paying attention to the regularity of its main triple cannon and firing as much as I could between two such shots). I like the fact it's linear at the beginning (as you use the path to go to the bad people hideout), and at the end (it's the last line to the finish), though it would have been better if there was a longer non-linear part at the middle (making both linear ends less long to compensate), and/or if you did not have to do things in a set order in there, I like for instance things like the two doors that guard the gate to the Factory from the Wasteland in the main game, which you can go and disable in the order you like, and of course the stars which you can grab in the order you like (in fact, the thing I prefer are things like the 8 levels in the original Legend of Zelda, which were meant to be made in that order, but in fact could be completed in a different order to an extent, though of course it is safer to do them in the normal order; in later Zelda games they unfortunately enforced completing the levels in a set order, by making each level require you to have completed the previous one or at least gotten the upgrade from the previous one, and when you've started a level you might as well complete it so you basically had to do them in order; so in a nutshell, what I like best is having a suggested order in which to do things, which I can ignore at my own peril).
To enter the secrets debate, well, I didn't find any at first (guess I'll have to find them now ). The end sequence is very good, but didn't indicate me at all that there were pending secrets (I just imagined that the elder sketch was someone from the characters of Sketchtopia that one would see in a future level and/or the SketchFighter academy). I mean, it's not like it's hard* to have a text sprite that would say that not all secrets have been found (like the main game does when you complete it without getting 100% stuff). I can't remember how Kingdom Hearts did that (my brother played it, not the 2 though), but I think it was better said at the end that there was special things if you really did find everything (I also remember that my brother, to find everything, used the strategy guide; I don't think you can reasonably get a strategy guide written for tCoC ;)). As for how well they are hidden, well, I like my secrets well hidden (and my easter eggs too, for instance once I let my little brother and sisters looks for them in the garden, and once they were done I went to look for those they didn't find because I was only interested in the ones that were really hard to find, unfortunately there was only one such one left), but not too problematic to find: like I implied in the topic about "maze", I don't like secrets which require you to hump kilometers of walls in FPS, and even less if you have to hit them in SketchFighter since that actually costs you life, and life is actually pretty hard to come by in tCoC; jump everywhere in a Mario game, sure, jumping is cheap, browse and, even worse, hit all walls (especially as you're vulnerable when doing so), no. Not that I won't try to find them now (in the game, only using the editor as a last recourse), I like replayability by secrets, it allows to view all the stuff with a renewed eye, but some cryptic hints (perhaps given at the end if you've found the secret in question) wouldn't hurt (:cryptic grin:, oh how you would love Voidspace ). By he way, how many such secrets are there, so that I know when I've found them all?
Other than that, a few, more technical, shortcomings: I've seen a non-solid metal plate (can't remember exactly where it's one embedded in a wall with another, solid this time, metal plate next to it). Also, other save rings do reappear after a save/die/reload cycle, I dunno if it's possible to have them not reappear, but assigning an unused, unique Extra2 value to each of them would I think prevent that (can't check that you did, I don't want to open the level with the editor).
*About how to do that: you could create a text sprite, copy it as many times as you have such secrets, give each of them the Extra2 value of the secret upgrade that matches it, and have all of them superposed on top of each other, but that would defeat the text antialiasing; instead you could put black masks between each two text sprites, the mask sprite going away when discovering the secret matching the text sprite just above, so that one and only one is visible as long as you've not found all secrets, but that would be limited by the number of layers, it should be possible to come up with a better layering where not all such text sprites are superposed, or even have them different (say if they give the hint for the secret they match); of course everything is simpler if the player is allowed to see all them at the end. As for how to disclose the "you've found everything go left for super-cool extra stuff!" message, it's even easier, just have as many black masks as there are secrets above that message and there you go, you can even make the way to the supercool extra stuff completely unconspicuous by simply having it protected by as many super force fields as there are secrets, just like the super force fields that prevent the player from going left and right at the end, thus making it impossible to suspect there is anything until they are all gone and the message is disclosed.