IMSSL — Official League Rules

Last Updated: March 2026

1. League Overview

The International Mario Super Sluggers League (IMSSL) is a competitive Mario Super Sluggers league built around individual player achievement within a 2v2 team format. The IMSSL is an open, ongoing league — there is no fixed schedule or predetermined bracket. Players compete freely throughout the season, and standings reflect each individual's cumulative performance across all matches played.

2. Membership & Roster

• The IMSSL has no fixed roster size. The league begins with a founding group of players and remains open to new members throughout the season.
• Players may join the league at any point during the regular season. Upon joining, they enter the standings with a 0–0 record.
• Players may leave the league at any time. Their recorded wins and losses remain in the official standings.
• There is no minimum number of games required to participate in playoffs, though a minimum may be established by league consensus prior to the postseason.

3. Game Format

• All IMSSL matches are played in 2v2 format. Each match involves two teams of two players.
• There are no fixed partnerships or assigned teams. Any two players may team up against any other two players in any given match.
• Matches may be 5 to 9 innings in length. The inning count must be agreed upon by all four players before the game begins.
• All games must be played with no CPU-controlled characters on either team. All roster slots must be filled by human-selected characters only.

4. Character Selection

Before each match, both teams must agree on one of the following two character selection methods. Both teams must use the same method — mixed methods are not permitted.

Option A — Random Selection

• Both teams randomize their full roster.
• Each team is entitled to one (1) re-randomization of their entire roster. This must be used before the game begins.
• Individual character swaps are not permitted under Random mode.

Option B — Snake Draft

• Teams take turns selecting characters in a snake draft order (e.g., Team A picks 1st, Team B picks 2nd and 3rd, Team A picks 4th and 5th, etc.).
• Draft order is determined before selection begins (e.g., coin flip or mutual agreement).
• All selections are final once made. No trades or substitutions are permitted after the draft concludes.

5. Illegal Pitches

Certain pitchers in Mario Super Sluggers possess pitches — such as changeups or curveballs — that exit the visible area of the screen after being thrown, making them effectively unhittable. These pitches are banned in all IMSSL play.

Rule:

• If an illegal pitch (one that exits the visible screen) is thrown, it must be ruled as an intentional ball.
• If the illegal pitch was thrown unintentionally, the pitcher must either:
  • Declare the pitch an intentional ball immediately, or
  • Throw an intentional ball on the very next pitch.
• Repeated or deliberate use of illegal pitches may be subject to review under the Amendments process (see Section 9).

6. Regular Season Standings & Scoring

The IMSSL uses individual player standings. Wins and losses are credited to each player personally, not to a team pairing. Each match results in a win for both players on the winning team and a loss for both players on the losing team. Ties, if they occur, are recorded as a tie for all four players.

Scoring System

Player scores are calculated from three components:

1. Participation Points (per game played, tiered by total games played in the season)

2. Win Points

2 pts per win, flat.

3. Win% Bonus

A one-time seasonal bonus based on overall win percentage. Requires a minimum of 4 games played to qualify.

Total Score = Participation Points + Win Points + Win% Bonus

The tiered participation rate rewards regulars without letting pure volume dominate — a casual player who wins frequently can still rank competitively against someone who plays every week but loses often. The 4-game minimum for the Win% Bonus encourages players to show up at least a handful of times to stay in contention.

Standings Tiebreaker

1. Most Wins
2. Higher Win Percentage
3. More Participation Points
4. More Home Runs Hit

7. Playoffs & Championship

• The playoff format will be determined by league consensus prior to the end of the regular season, based on the number of active players at that time.
• Seeding for the playoffs will be based on regular season winning percentage.
• Specific tiebreaker rules for playoff seeding will be established alongside the playoff format.
• Playoff games may adopt different rules (e.g., fixed inning counts or draft requirements) if agreed upon by the league before the postseason begins.

8. Statistics & Record Keeping

• At minimum, each player's win-loss record must be tracked for standings purposes.
• The league is encouraged (but not required) to track additional statistics such as runs scored, home runs, and batting average.
• It is the responsibility of the participating players to report match results to the designated record keeper after each game.
• Disputed results must be raised before the next match is played and resolved by league consensus.

9. Amendments

• Any active IMSSL member may propose a rule amendment at any time.
• Amendments are adopted by majority vote of active league members.
• Amendments take effect at the start of the following match after adoption, unless the league agrees to immediate implementation.
• All adopted amendments will be recorded in this document with the date of adoption.

The IMSSL is built on competition, creativity, and fun. Good luck to all participants this season. ⚾