Mix a color and watch its hex code build itself — then run it backwards: read a hex code, predict the R, G and B numbers, and only then reveal.
A hex color code is six characters that are really three separate bytes — two hex digits for red, two for green, two for blue. This tool runs that conversion in both directions, one panel each.
Panel 01 — mix to hex code. Drag the R, G and B sliders. Each channel is one byte, a number from 0 to 255, and beside its decimal value are the same number's two hex digits. The swatch and the combined #RRGGBB code update as you drag, and the note underneath spells out the arithmetic for the strongest channel: 194 = C2, because C is twelve sixteens (192) and 2 adds two more.
Panel 02 — hex code to RGB. A hex code appears with no color attached. Work out a decimal value for all three channels before you press Reveal. That order is the whole exercise: reading the answer teaches almost nothing, but committing to one first tells you exactly which conversions you can actually do. The reveal shows each channel's true value, your value, and the signed difference. Press Next code for another.
Do the hard direction as first digit × 16, then add the second. The codes with letters in them are the ones worth hunting for — A=10, B=11, C=12, D=13, E=14, F=15 — because that is where base 16 stops looking like base 10.
Nothing here is graded and the running tally is yours alone. The skill carries straight out of color: a MAC address is six bytes written as twelve hex digits, and each hextet of an IPv6 address is read the same way.
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