8-bit style bouncing ball around a canvas
Bash + Unix utilities, 125 117 bytes

for((x=y=u=v=1;;x+=u,y+=v,u=(x&lt;1||x&gt;=`tput cols`-1)?-u:u,v=(y&lt;1||y&gt;=`tput lines`-1)?-v:v)){
tput cup $y $x
sleep .1
}




Animation of sample run: