Two decks, one board, two jobs: race four color foundations up while you stitch four full 13-card runs, Spider-style.

Rouge et Noir Solitaire is French for "red and black", and the name describes the game's split personality. It is a two-deck hybrid with two jobs at once: build four foundations up from ace to king in matching colors, Klondike-style, while assembling four complete 13-card sequences in alternating colors, as in Spider.
Because every card must end up in one camp or the other, you're constantly deciding whether a card should climb a color foundation or stay in the tableau as part of a growing red-black run. Each stock deal drops a card onto every tableau pile, burying whatever you had lined up, so timing those deals matters. Rouge et Noir is challenging, with only a moderate chance of winning, and skill counts for more than luck here.
Rouge Forty Solitaire and Spider Solitaire both build on that same alternating-color sequence idea.
From here, the classic Solitaire is the natural next stop if you'd rather juggle one job instead of two.
If you run into anything odd or have an idea that would make the game better, please contact me.
Enjoy playing!
4 color foundation piles: Build up from Ace to King in the same color, in two pairs; each pair must start with one red ace and one black ace.
4 sequence foundation piles: Each accepts only a complete 13-card sequence, King down to Ace in alternating colors, moved whole from the tableau.
10 tableau piles: Dealt in a staircase of 8, 7, 6, 5, 4, 3, 2, 1, and 1 cards with only the last card of each pile face up; the tenth pile starts empty. Build down in alternating colors.
Stock: Click to deal one face-up card onto every tableau pile. There is only one pass and no redeals.
There are eight foundation piles of two kinds.
The four color foundations sit in two pairs. Each pair must begin with an ace of each color, and a card can be added only if it's one rank higher and the same color as the pile's current top card — so either red suit may continue a red pile. These piles run from Ace up to King, and their top cards may be moved back to the tableau.
The four sequence foundations start empty and accept only a finished 13-card run, King down to Ace in alternating colors, built in the tableau and moved across in one piece. Once placed, these cards can never be taken back.
To win, complete all eight piles: half the pack climbs the color foundations and the other half forms four full sequences.
Ten tableau piles dealt as a staircase from eight cards down to a single card, plus one empty space; only the top card of each pile is dealt face-up, and buried cards flip as they are uncovered.
A card can be added to a tableau pile only if it's one rank lower and the opposite color of the pile's current top card, so the only cards that fit on a black 8 are the red 7s.
Face-up cards in a proper alternating-color sequence may be moved together as a unit.
Empty tableau spots may only be filled with a King or a sequence headed by a King, from any pile.
There is no waste pile; the remaining 67 cards comprise the stock.
When you click on the stock, one card is dealt face-up onto every tableau pile, covering whatever was there — so tidy your sequences before dealing. There is only one pass through the stock, and the final deal may not reach every pile.