420

INTRODUCTION

Players sit across from each other at an initially cleared table. The two players, Red and Blue, take turns maintaining a hand of four dice of their own color. Mark Steere designed 420 in September 2025.

PLAY

Starting with Red, players begin by rolling all four of their own dice, forming their hand. On each of your subsequent turns, you must reroll 1, 2, 3, or 4 of the dice in your hand, and add them back into your hand - one roll per turn. (See REROLL RESTRICTIONS below.)

OBJECT OF THE GAME

The goal is for the dice in your hand to total exactly 20. No more, no less. For example, (6, 5, 5, 4) is a winning hand. It's possible to win the game on your first turn, with a probability of 2.7% - about 1 in 37 plays.

REROLL RESTRICTIONS

• ..4 dice: You can always reroll 4 dice.
• ..3 dice: You can only reroll 3 dice if the remaining die has a value of at least 5.
• ..2 dice: You can only reroll 2 dice if the remaining 2 dice sum to at least 10.
• ..1 die: You can only reroll 1 die if the remaining 3 dice sum to at least 15.

GO OVER AND RESET

If your hand sums to 21 or higher, on your next turn you must reroll all four of your dice (reset).

MONOCOLOR 420

Each player must have their own hand but not necessarily their own color. All of the dice can be standard white dice with black pips for example. Just try to keep the hands separated if they're all the same color.

MULTIPLAYER 420

420 can actually accommodate any number of players. Randomly choose Player 1. Succeeding turns proceed clockwise. In successive rounds, the new Player 1 is to the left of the previous Player 1. The round winners drop out, and the last remaining player buys the drinks.

DESIGN NOTES

I wanted to invent a simple dice game. No score sheet. No poker chips. Just dice. And then simple rules. No combinations to memorize. No bids, no bluffs... No showdowns or tiebreakers. But I also wanted strategy, which 420 has. I had never heard of pub games, but to my surprise, 420 turned out to be a classic pub game. Easy to learn, easy to play. A lot of luck, and a little strategy. Short duration. Nobody wants to think too hard or wait too long for their next drink. I’m really glad to have a pub game, now that I know what they are.

STRATEGY

You have to balance your risk against the quality of your opponent‘s hand. For example, say your opponent has (6, 5, 4, 1) - an ideal hand with a foundation of 15, and a single die. She would keep rerolling the 1 until either winning or going over. And say you have (6, 5, 5, 1) - not an ideal hand. It has a foundation of 16. Should you reroll your 6 and 1 to try to form an ideal hand? Or just reroll the 1? Just the 1. You don’t have time to go back and try to form an ideal hand, because your opponent already has one. Now consider the same problem, but this time your opponent has (4, 3, 3, 2). Now you would reroll your 6 and 1, because now you have time to try for an ideal hand. And there may be more complex problems involving a choice between rerolling two dice or three dice.

REROLL NOTE

Select the dice to reroll by clicking on them. The unselected dice will remain.