The game features a rudimentary battle-system that is based on a card-game system:
Each turn you draw cards and play them for their energy-cost. Once you played all the cards you wanted/can you end the turn - and the enemy attacks. If the enemy reaches 0HP it is defeated and you get a reward.

There are 6 basic types of cards:

• Weapons
  
• Healing
  
• Energy-Reduction
  
• Drawing
  
• Blocking
  
• Reflection

and they come in 4 rarities:

• Common
  
• Uncommon
  
• Rare
  
• Legendary

Higher rarity in general means better items

They are the bread and butter of actually defeating the enemies. Activate them and the monster loses health according to the attack reported on the card.

Heals you for a percentage of your health. Can not heal you to more than 100% of your max-health

Reduces the energy-cost of the NEXT card you play. Will not carry over to another card.

Draws the stated number of cards - up to the maximum hand-cards you can hold

Reduces the next attack of the monster by the given amount. Does not carry over.

Reflects parts of the monsters next attack-damage back. Does NOT reduce the damage you take.

New the main focus of this guide:
WEAPONS

There are a total of 10 weapons:



So really notably are 4 weapons:

They are just bad. Being a common weapon and barehanded this is to be expected - but there is zero reason to ever keep this card, let alone upgrade it as it is the weakest of all weapons with no benefits what so ever.
It has the lowest damage from lvl 1 to lvl 10, but the same energy and upgrade cost as Rock.

the lowest lvl 1 damage of uncommon weapons - but once upgraded to lvl 5 it becomes the strongest. But you likely don't want to upgrade it anyways.

good damage and the same 2 energy cost as uncommon weapons - but it can only be upgraded to lvl 7.

Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out.

the mother of all weapons:
it starts strong and only gets better with upgrades - up to lvl 9 it is exactly the same as the Plasma gun but at lvl 10 it deals slighty more damage