I'm getting careless, likely distracted by yesterday's event. I was attacked by zombies while away from my main stash of food. I reacted immediately and was able to minimize my losses, fortunately, but I really need to get a grip on myself. Next time might not be this easy.
(You lose 10% (fractions rounded up) of your current Food, and take 2 points of damage from minor scratches.)
The Ballista is a slow-moving, slow-firing artillery unit suited for ranged attacks against buildings and heavy infantry. Ballistas have better range if fired from elevated ground, raining death on unsuspecting enemy units. Ballistas are expensive, costing 200 Wood + 100 Stone each to train, so make sure you protect them from enemy Skirmishers. Possible upgrades include attack range, rate of fire, splash damage, splash radius and incendiary projectiles. Ballistas can be upgraded to Trebuchets once you research the Mathematics technology.