Guillan reckons fog and roof levels can be particularly tough, but progress can be eased using certain plants. For fog levels, he explains you can use night plants, so make the most of that: "Planterns protected by Pumpkins are your best friends here, because they'll help you see. Blover does get rid of the fog, but you need 100 suns to buy one plant."
For roof levels, most of the plants you'll have used to that point will no longer be useful, so you'll need to build a strategy around '-pult' plants, such as Cabbage pult, Kernel-pult and Melon-pult.
"Level 5 of the roof stage is one of the toughest in the game," he says. "To get through it, build two columns of Chompers, because they eat through zombies two rows away. Protect them with Pumpkins and save some Cherry Bombs, because they're great for 'Damn it, I need to kill some zombies quick!' panic moments."
Although Adventure Mode is the main mission in Plants vs. Zombies, there's plenty to do once your flora-based assault has bested Dr Zomboss. On the iPad, there's an endless survival mode, which Guillan says requires you to have "a good arsenal of plants before starting out," adding that those you can buy from Crazy Dave are hugely useful here.
He also provided tips for three of the mini-games that can be found lurking in the 'More ways to play' section…
I, Zombie: This is a puzzle mode where you 'plant' zombies rather than plants. To begin with, target sunflowers and keep an eye out for Magnet-shrooms and Threepeaters. When a plant is in your way and messing with your strategy, use a Bungee zombie.
Vase Breaker: Here you smash vases, and each releases a plant or a zombie. Although you need good luck, success also depends on keeping your defences balanced - don't put plants in the middle and don't break too many vases too quickly. Also keep in mind that the Squash is a great ally, because it can take down multiple zombies and Gargantuar!
Slot Machine: Another slightly luck orientated mini-game, Slot Machine gives you a sun target, but each spin costs 25 suns. You get plants for pairs (or better) in the slot machine, so initially keep using it until you've built a strong defence. Plant Sunflowers and Peashooters at the back, and protect them with Wall-nuts. Then stop spinning and start collecting suns.