This may be undocumented or something, but it's strange behavior none the less:
When Link is on top of an ffc, say ffc[9], and another ffc, say ffc[16](damage 1 heart) is moving through him, Link will take no damage.
A more visual example:
A 64x96 phantom boss that changes states between transparent(none), and normal(damage 2 hearts). While standing on the ffc(none) Link is basically invulnerable to any other ffc damage combos.
Well i've got another example but you get the picture.
edit* Just realized I think I had flags set too; Draw over in both cases....have to check others.
Yes. This issue was discussed some time ago, and modifying the engine to correctly blend all of the combo types Link is touching is too complex for pre-2.50.
By default, FFCs take priority over ordinary combos (I don't remember if higher or lower FFC numbers have higher priority). There is also an FFC flag, "Is Ethereal", which, when toggled on, makes the FFC completely transparent for purposes of combo detection. That is, if Link is standing on an Ethereal platform, he should get hurt by both your custom boss, and any damage combos he travels over.
Aaahhhh!!! So THAT's what the "ethereal" flag does. Damn, I knew that was somehow important to know. Thanks... Okie dokie then, Bye, bye bug.