Developer PopCap Games can't be accused of throwing Plants vs. Zombies 2 together quickly just to capitalize on the popularity of the original. As expected, the subtitle It's About Time is not only about the exacerbated wait fans have had to suffer, but about the sequel's new time-traveling premise.

Crazy Dave returns, discovering a hot sauce that perfectly complements the taco in the original game. It was so good that he wants to eat it again, so he channels Back to the Future and invents a time machine so he can go back in time to do just that. Thus begins a new adventure.

While the original kept the player within the confines of his or her home, players will now be teleported to various themed areas throughout time. We got a look at the first three epochs that Crazy Dave will be visiting, from Egypt, to the pirate seas of the 1600s, to the Wild West. All the zombies in these areas are dressed in appropriately themed garb, and each still have specialized strengths and abilities. There will also be some new zombies added based on the theme of the map, such as a parrot-totin' pirate zombie that can steal plants.

Each era will feature a global map that takes the player through its various stages. The main adventure mode missions will drop random keys that will unlock separate areas for challenges and mini-games off the main track. Egypt, for example, had 11 main missions, and 10 "side-quests." Completing these side quests can unlock new plants and items.

PopCap said each era will have more than 20 areas to complete. Completing the main set of missions will allow the player to enter a stargate to travel to the next time period. Once a player completes the time period, a challenge mode opens where the player can play levels over and over, much like survival mode in the original game. Players can earn stars by completing objectives in subsequent trips through a level.

The layouts of levels will also be a bit more diverse. For example, a pirate-themed level had what looked like two ships joined by a long two-row plank. The areas on either side of the plank were inaccessible--zombies could only cross to the other side on the plank. But some mechanics can be used to get around the missing sections, such as the player firing cannons across, or zombies swinging across on a rope.

Going up against new zombies means players will need a new arsenal of plants, and while many of the old favorites will be returning, about 15 more have been added. New plants include the coconut cannon, which fires an area-of effect explosion, and the bonk choy, a more powerful take on the original's split pea. Our favorite was a snapdragon that breathed fire into several lanes at once, consolidating the popular combination of threepeater and torchwood.

In addition to new plants, the gameplay has been tweaked a bit as well. Not only will you be tapping the screen to collect sunshine and coins, you'll also collect plant pellets. Collecting these will fill up a super meter. When full, players can choose a plant to upgrade. For example, a pea shooter can become a machine gun, or a sunflower can become a nuclear generator of sun energy. The use of plant food basically eliminates the need for variations of the same plant, such as the gatling pea and spikerocks in the original game. This tweak also demands a bit more strategy, as power-ups only work for a limited time and should be used at appropriate times.

Additional power-ups will allow players to directly assist in the zombie killing. "Power Pinch" allows players to pinch zombie heads. "Power Toss" will allow players to flick zombies off the board. Finally, "Power Zap" can electrocute the undead.

Unlike the original, Plants vs. Zombies 2 will be free-to-play, and it's clear that PopCap has designed the game around supporting that economy. Players can purchase plant food with in-game coins at any time during a level and as often as you have cash. Power-ups can also be purchased with in-game coins. While this approach often can be predatory, it was rather easy to earn in-game coins; I didn't feel forced to spend any real money, although it's impossible to extrapolate how the final game will be balanced based on a preview.

Plants vs Zombies will launch July 18 on iPad, iPhone, and iPod Touch. The three eras mentioned will be included at first, and more will become available as DLC after launch.