Abilities

Abilities are a ScrapTD feature unlocked at Level 5. You can select up to 3 different abilities at the same time (in the past you could use the same ability in more than a slot) in combat against your opponents, but your opponent must be Level 5 or higher too in order to be able to use them.

Abilities
There are currently 9 abilities available, all automatically unlocked when getting to Level 5.

Strategical use
The best abilities are Scrap, Faster Barrels, Freeze and Defense Boost. The rest of the abilities aren't bad, they're overshadowed by these four. Blind is excellent too in the lower arenas, but against skilled players it can backfire, as the opponent can still use abilities while the player's blind is active.

The heart abilities require no skill or strategical thinking at all, but they are also the weakest abilities. On the other hand, Double Barrels is hard to use well.

Changes over time
After the initial release of abilities, a lot was changed. Scrap originally gave 15 seconds and double barrels wasn't working, for example. The darkness ability became longer and longer, which made it actually worse, in 1.0 it was buffed a lot by increasing the effect. Other abilities have been buffed or nerfed too.