You are the sphere, not how you even stay sliding if you rotate. So if you slide to the front and then you rotate to the left you keep sliding to the front. Uhm, you see, I'm not good at explaining things, just look...
sync on
sync rate 40
autocam off
make object sphere 1,100
position object 1,0,0,0
make matrix 1,1000,1000,10,10
zwaarte#=0
speed#=0
do
if leftkey()=1 then yrotate object 1,wrapvalue(object angle y(1)-1)
if rightkey()=1 then yrotate object 1,wrapvalue(object angle y(1)+1)
if upkey()=1
speed#=10
xs#=object angle x(1)
ys#=object angle y(1)
zs#=object angle z(1)
endif
if downkey()=1 then move object 1,-1
speed#=speed#-0.05
if speed#<0 then speed#=0
x#=object angle x(1)
y#=object angle y(1)
z#=object angle z(1)
rotate object 1,xs#,ys#,zs#
move object 1,speed#
rotate object 1,x#,y#,z#
zwaarte#=zwaarte#-0.5
if object position y(1)<=0 then zwaarte#=0
if object position y(1)<=0 then position object 1,object position x(1),0,object position z(1)
if object position y(1)=0
if spacekey()=1 then zwaarte#=20
endif
position object 1,object position x(1),object position y(1)+zwaarte#,object position z(1)
position camera object position x(1),object position y(1)+110,object position z(1)
rotate camera object angle x(1),object angle y(1),object angle z(1)
move camera -140
sync
loop
