You can do the majority of those already.
Triple J wrote:A trigger to reverse the effect of Delta Orbs and Delta Negate Orbs - same with the Delta Negate Zones.
You can use "Move Item" to switch Delta Orbs and Delta Negate Orbs. I think something like this is used in the story mode somewhere.
Triple J wrote:A trigger to mirror items.
Item -> Scale Item -> Absolute -> set xScale (or set yScale if flipping over a horizontal axis -> "-1.0"
Triple J wrote:This might be too advanced, but how about something like "curses?" I.e. gradual health loss until you do/collect something; reversed controls; loss of attack power; one-hit deaths; limited jumps. Curses could be inflicted from enemies, events, or even items.
You can use "Move Item" to periodically move small invisible spikes to the player's position and then move them back.
Triple J wrote:This might also be too advanced, but maybe there could be some way to lose collected Squares, like from thieves, "anti-squares," ...or curses.
Math -> Subtract -> g_COINS = g_COINS - 1