1.5.5 changes:

-2 new unlockable towers!

-Airstrike Beacon range 456 > 472

-Fire Shooter unlock requirement 200 > 150

-Mark Turret's XP requirements per level have been reduced

-Temporary Sentry cost 125 > 100, materials dropped on destruction 50 > 25

-Enemy HP multiplier in Weekly mode 1.1x > 1.15x (this will take effect starting on Week 108)

-Railgun Turret damage 16 > 17

The grinder's levelup bonus was pretty weak, so it's received a noticable buff:

-Grinder pull speed per level significantly increased, 0.1 > 0.175

1.5.4 changes:

-Fixed indirect kills not counting towards Fire Shooter progress. This also meant that Mortars couldn't progress this at all since their projectiles never "directly" hit anything. Since this is now much easier to progress, requirement has been increased from 100 to 200

-Sniper player weapon upgrade damage 145 > 150, and is now semi-piercing (like Super Sentry Gun)

-Damage penalty for AOE towers in Arcade is reduced slightly: damage dealt 0.667x > 0.75x

-Proximity Mine cost 75 > 50

-The cap on health regen per second for Buff Pads increased from 40% to 50% of your max HP

-Bulldozer (slow, contact damage enemy) move speed very slightly reduced 1.9 > 1.8

-Fixed rare circumstances where a spawn would fail due to not enough space which froze the game (usually happened in Arcade on certain maps) if it cannot find a spawn it will spawn on top of structures or nearer the player as a last resort

-Spawnling base HP 23 > 25

-Tesla damage per charge increase per level 12 > 15 plus now they also gain a very small fire rate increase per level (-2 reload time frames per level)

-Pulse tower base damage increased 27 > 30

-Added frogs.