The first level of this game is a good simulation for how a gas giant can protect the inner solar system from heavy bombardment by meteors. As the gas giant (in this case, I giant meteor) gains mass, fewer and fewer meteors reach the planet, and those that do increasingly glance off the atmosphere. Eventually, the extinction rate reaches near-zero when the giant reaches its top mass, and with the heavy bombardment phase over, life can bloom. We can all be happy that Jupiter didn't then wobble out of alignment and destroy all life as we know it, as it did here!
The last level is easy with 4 rows of maxed out freeze traps followed by 4 rows of maxed out archers. No need to build barricades, nothing will reach your archers. Use the cannon-shotgun-arrows combo from BennyGreen and the occasional fireball on the frozen enemies from the freeze traps. Easy-peasy!
 "Dynetzzle"){kind=icon}
 "Effing Meteors"){kind=icon}
 "Siege Knight"){kind=icon}
 "Battle Beavers"){kind=icon}
 "Level Up!"){kind=icon}