Desyncs due to floats

[Kvel2D]

Read about this topic here: https://gafferongames.com/post/floating_point_determinism/

Possible desync scenario

Peer 1	Peer 2
Creep moves to new position	Creep moves to new position
position.x of creep changes from A to B	position.x of creep changes from A to (B+C), where C is some very small number like 0.0000001
Creep is inside the range of tower which is about to attack	Creep is outside the range of tower which is about to attack
Tower attacks creep and kills it	Tower doesn't attack creep, creep lives and reaches portal

From here, any kind of divergence is possible. Creep may drop an item for Player 1, so now one client thinks player 1 has an item, while another client disagrees. Towers will have different exp values and levels.

Test 1

Build an Icy Skull tower to slow creep. Compare history of positions.

Got same positions on both peers:

338 pos=(216.477600,-1183.599731), speed=204.441416
339 pos=(209.724274,-1180.161987), speed=204.441416
340 pos=(202.390930,-1176.428955), speed=222.000000
341 pos=(195.057587,-1172.695923), speed=222.000000