1. click on the "water" to paste a fish
2. hit the Start Button
3. increase the speed to max by moving the bar to the very right
4. after the field has filled up with fishes hit the Pause Button
5. in the paste-dropdown-menu select "one shark" instead of "one fish"
6. click on a fish on the screen to paste a shark instead
7. hit Start again and see how almost all fishes are eaten...
8. hit Pause and increase the grid's size to about 100x100
9. click "update screen" to apply the size
10. paste some fishes and hit Start again
11. Before it gets boring pause and paste some sharks
12. press Start - now always some individuals should survive
13. since you can't see the animations now check the "timecourse" box, now

• the fishes are green, light green meaning: ready to produce a child, dark green for those who just had a birth and all shades inbetween for pregnancy
• the sharks are red, light red meaning: "I just had a tasty meal" and dark red for "I will starve next turn" and -again- all shades inbetween

Finally change the three numerical values - maybe you increase fish pregnancy to 20 or even 30 and reduce the sharks pregnancy time? (Increase grid size to 150x150 to prevent extinction of one species)