How can I get my while loop to run until my condition in my if statement is met? (In MATLAB)

clc%clears screen

clear all%clears history

close all%closes all files

format long

%Euler's Method

%Initial conditions and setup

%Projectile motion

x=3;%randi(3);

y=3;%randi(3);

figure('color','white');

plot(x,y,'bo');

hold on

wind = (-10 + 20*rand(1));

fprintf('The wind speed is %2.2i ',wind);

v0= input('Initial velocity(m/s): ');

a= input('Angle of projection(in degrees): ');

a=a*pi/180;

h=.01;

cd=.1;

%cdy=.1;

%cdx=(rand*2-1)/2;

%cdy=(rand*2-1)/2;

m=1.5;

g=9.8; %acceleration due to gravity in m/s^2

%td=2*v0*sin(a)/g; %total time

x1=0;

y1=0;

t=0;

r=4;

while y1 >= 0 %y1 >=0

plot(x1,y1,'o','MarkerFaceColor','b','MarkerSize',8)

hold all

xlabel('Distance in meter');

ylabel('Height in meter');

xlim([0 30]);

ylim([0 30]);

getframe;

fd=(v0*cos(a))*cd+(wind);

x1=x1+(h*(v0*cos(a)+ fd*t));%(cd*t + wind))); %Euler's method for x

y1=y1+h*(v0*sin(a)-g*t-(cd/m)*t); %Euler's method for y

t=t+h;

if abs(x1-x) <= .25 && abs(y1-y) <= .25

fprintf('Congratulations you hit the target!')

break

end

end