Every spot on a grid has an address: (x, y). Go along first, then up. Plot points, follow treasure maps and beat the clock.
Start here. A grid is like a city map. Every crossing has an address of two numbers in brackets, like (3, 4). The first number says how far to go along the corridor (that is x). The second number says how far to go up the stairs (that is y). Along first, then up.
Why the order matters. (3, 4) and (4, 3) are two different places. A good way to remember: you walk before you climb, and x comes before y in the alphabet.
Axes. The flat line along the bottom is the x-axis. The upright line on the left is the y-axis. They meet at (0, 0), called the origin. A point on the x-axis has y = 0, and a point on the y-axis has x = 0.
Below zero. Extend the axes past zero and the grid has four parts called quadrants. Going left makes x negative, and going down makes y negative. Quadrant I is (+, +), II is (−, +), III is (−, −) and IV is (+, −). A mirror image over the x-axis changes the sign of y, and over the y-axis it changes the sign of x.
Try this above. In Play, tap (2, 5) and then (5, 2) and watch the two paths. Then switch to "Challenge me", tap (−3, 2) and press Walk there. Which direction did the walker go first?
Start at the origin (0, 0). Go 3 steps along to the right, then 4 steps up. You land on the point (3, 4).
The two axes cut the grid into four quarters. Each quarter is a quadrant. Quadrant I is top right, II is top left, III is bottom left and IV is bottom right.
"Just starting" uses a small grid from 0 to 6. "I know the basics" uses 0 to 10. "Challenge me" adds negative numbers, from −5 to 5.
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