Linear World Cup

A soccer game where you score goals and complete passes by writing the slope-intercept equation of the line connecting your player to a teammate or the goal. Choose a proportional (y = mx) or non-proportional (y = mx + b) mode, play against the computer or a friend, and compete in a full tournament bracket. Controls: type digits for the slope numerator, denominator, and y-intercept, minus key or on-screen button to toggle negative, enter to kick, mouse or the on-screen keyboard to play on any device.

Teaching Notes for Educators

Linear World Cup covers the full slope-intercept unit - writing y = mx + b, distinguishing proportional relationships (b = 0) from non-proportional ones, and reading slope as rise-over-run - by making the equation itself the only way to move the ball. Every pass and every shot requires typing a real slope (as a fraction) and a real y-intercept, then watching that exact line get drawn across the field, so students see immediately whether their equation was geometrically correct, not just numerically close.

Proportional vs. non-proportional, built into the mode select. The PROPORTIONAL mode locks b = 0 and only asks for slope, isolating that skill before NON-PROPORTIONAL introduces a real y-intercept - mirroring the exact progression CCSS.8.EE.B.6 describes from y = mx to y = mx + b.
The ball's position is the y-intercept. Since every pass starts from x = 0, the ball's current coordinate is always (0, b) - so a wrong y-intercept guess is caught instantly as "incorrect y-intercept," reinforcing what b actually represents on the graph rather than treating it as an abstract constant.
Slope entered as a true fraction. Students type a numerator and denominator (with a sign toggle), not a decimal, which keeps rise-over-run reasoning front and center and prevents rounding from masking a conceptual error.
Three support levels for differentiation. EASY shows a live preview of the line as it's typed, HARD hides that preview (and shifts the y-axis numbering so answers can't be eyeballed from familiar values), and 2-PLAYER turns review into a head-to-head match for two students sharing a screen.
A computer opponent and a tournament bracket. Matches against the AI and an eight-team single-elimination tournament give repeated, game-like reps of the same skill without a lesson ever feeling like a worksheet.
Immediate geometric feedback. A missed pass or shot draws the actual line the student's equation describes, so "the ball went to the wrong place" is always visibly traceable back to which part of the equation - slope or intercept - was wrong.
Low-stakes, replayable practice. No accounts, no penalty for a wrong equation beyond losing possession, and an on-screen numeric keypad so the game works identically on a classroom tablet or a touchscreen Chromebook.