My son could verbally identify 10 colors and lots of shapes at 18 months. At two-and-a-half years, I taught him to recognize the alphabet and letter sounds. A year later, he watched five episodes of a PBS show called Reading Between the Lions
and after that he could read any three-to-five-letter-word and spell them, too. At that time he also "read" numbers as if they were letters. For instance, he would translate "5826" into the word "FETS." He'll also turn life into simple math problems. (5 jelly beans become 2+2+1 jelly beans to him).
But now that he's four, he's lost all interest in reading. He likes when I read both fiction and nonfiction to him (about dinosaurs and snakes) but he prefers movies, like Jurassic Park and Godzilla. Is he gifted or just well-taught? I've heard that gifted kids are instantly voracious readers and teach themselves to read.
You are describing a wonderfully creative and intellectually playful little boy. Not all gifted children are early and advanced readers. Your son's intellectual puzzlers and playfulness are quite indicative of a very bright child. At this point, why worry if he is gifted? Keep reading with him, talking with him, "playing" math and language games, and watching movies -- especially real-life documentaries that he would love, like those on the nature and animal channels.
Also, please remember that each child has an individual learning style. It seems like your son is highly visual and enjoys the visual stimulation of pictures, color, and movement. He may really enjoy animated computer math games, and reading software that has lots of color pictures. With new technology, "reading" can be more and more like going to the theater! Keep learning fun for your son and support his creativity. If at some point you want to determine if he should be formally identified as gifted, you can request that he be evaluated. At this point, enjoy him!