These are two very interesting self-working effects, both based on topological principles. You do not need to learn any math or remember a whole lot to perform these two stunning effects. (These two effects have been taken from Shane's books Automata and Pentalogy.)
A packet of cards, the twenty cards making up a royal flush, is given to a spectator to shuffle. The spectator then chooses one of the values (say, for example, Jacks), and the cards mixed so that some are face up and some face down. The packet is further mixed by the spectator, eventually being divided into piles and then the piles mixed face up and face down again. Despite all the mixing, shuffling, and cutting, all the cards are shown to have turned face down except the four cards matching the spectator's selection, the Jacks.
A Line Much Too Thin
This effect is Robert Neale's "Trapdoor Card", but with a different presentation, one which I personally like better, because the presentation is clearer and easier to sell than Neale's original one. I remember, many years back when I started to get seriously into magic, the "Trapdoor Card" was one of my first effects I performed. Anything clever based on mathematics still has a tremendous appeal to me.
1st edition 2006; 20 pages
word count: 7342 which is equivalent to 29 standard pages of text