% INITIAL CONDITIONS
% Set initial conditions for the puck.
x0 = 0.15; % Initial horizontal position of the puck, in meters.
y0 = 0.10; % Initial vertical position of the puck, in meters.
vx0 = 0.2; % Initial horizontal velocity of the puck, in m/s.
vy0 = 0.0; % Initial vertical velocity of the puck, in m/s

% Put initial conditions together into a column vector.
X0 = [x0; y0; vx0; vy0];

%% DEFINE PUCK AND ENVIRONMENT

% Set the parameters of the puck and the environment as global variables,
% so that this function can plot them and the state_eq function can access
% them for computing the motion. Whenever you refer to any of these values,
% you should use the variable names, not the hard-coded numbers, so that
% changing them here changes them everywhere.

% PUCK
% The puck is modeled as a particle with a fixed mass.
global PuckMass;
PuckMass = 0.155; % Puck mass, in kilograms.

% WIND
% The wind is a vertical stripe that always pushes the puck in the
% vertical direction.
global WindStartX WindEndX WindStrength;
WindStartX = 0.3; % Horizontal position of the start of the wind zone, in meters.
WindEndX = 0.5;    % Horizontal position of the end of the wind zone, in meters.
WindStrength = 0.02; % Vertical strength of the wind, in newtons.

% SUN
% The sun is a circular zone that applies thrust to the puck.
global SunCenterX SunCenterY SunR SunStrength;
SunCenterX = 0.75; % Horizontal position of the sun's center, in meters.
SunCenterY = 0.4; % Vertical position of the sun's center, in meters.
SunR = 0.15;    % Radius of the sun, in meters.
SunStrength = 0.03; % Strength of the sun, in newtons.

% WATER
% The water is a circular zone that makes the puck turn to the right.
global WaterCenterX WaterCenterY WaterR WaterStrength;
WaterCenterX = 1.2; % Horizontal position of the water's center, in meters.
WaterCenterY = 0.7; % Vertical position of the water's center, in meters.
WaterR = 0.2;       % Radius of the water, in meters.
WaterStrength = 0.05; % Strength of the water, in newtons.

5. A N-by-N diagonal matrix is one of the form d 1 d2 , d N...