The positive attributes of the character Old Man are -25% enemy speed and +10 harvest.
A neutral and therefore very unusual property is that the map size is -33%, as this can be an advantage, since the opponents are more in a pile, making it easier to attack and the materials can be collected faster, as well as from it can be a disadvantage, since you can be overrun much more easily.
Another neutral property is that -10% fewer enemies spawn overall, which of course automatically means fewer materials.
The negative trait is that the Old has -10% Speed.
Due to the smaller map, it is ideal to concentrate on tools and turrets, as these can unfold much better in a smaller area.
Therefore, start the run with the Wrench.
In terms of damage, focus solely on engineering and other turrets that can support your turrets that you get from the weapons even more, since the other stats have no effect on your turrets.
Defensively, get sufficient max HP, Health Regen and Armor.
Other items that slow down the opponents even more are very helpful, because otherwise you can unfortunately be overrun by the opponents more easily.
Since you start with 10 harvests and this increases automatically from the first wave, it is also a very good choice to invest in this value so that you have a lot more materials at the end of the wave after a very short time.
In addition, this also compensates for the fewer opponents very well, which means that you also have fewer materials.
The Old's simple way of playing makes it very easy to complete the run, even on higher levels of difficulty.
If you finish the run with the Old, you will get the item snail, which was once much stronger and has been nerfed, but is still a good choice to reduce the speed of the opponent.