Hard mode tip: Use raptor to block ground forces.
For level 10, use your subs and boats to attack flaks and the long range boat. You can bomb the rest (subs and tank-like boats) later when the air is clear. Use your raptors to clear the bombers, and use raptors to block ground troops at choke points.
This game is hard, but it teaches good concepts. The strategy is to lock down the country with road blocks and closing all airports and seaports. Note that Washington is not infected for the first few seconds and its seaport should be closed down immediately. Add 2 roadblocks for Florida and one for oregon and you are set. If you need cash, it's better to leave mexico's borders open than canada, although it's possible to complete the game on hard without closing both. But airports, with >3% chances of infections must be closed immediately.
 "JumpingLine"){kind=icon}
 "Jelly Escape"){kind=icon}
 "Psychout"){kind=icon}
 "DuckLife 4"){kind=icon}
 "Bullet Time Ninja"){kind=icon}
 "Bela Kovacs and The Trail of Blood"){kind=icon}
 "Road of the Dead"){kind=icon}
 "Robot Wants Ice Cream"){kind=icon}
 "Vertical Drop Heroes"){kind=icon}
 "Kingdom Days Sim Date"){kind=icon}
 "Who wants to be a millionaire??? (the game)"){kind=icon}
 "Level Up!"){kind=icon}
 "Perfect Balance 2"){kind=icon}
 "Battalion: Ghosts"){kind=icon}
 "Blockpolis"){kind=icon}
 "Pandemic: American Swine"){kind=icon}