Fix

code/__DEFINES/inventory/carry_weight.dm

@@ -43,7 +43,6 @@
 /// How penalizing the default penalty curve is; lower is weaker slowdowns from overweight.
 #define CARRY_WEIGHT_SCALING 2.5
 /// For now, constant - bias factor; higher = skip more of the curve as soon as weight goes above strength
-
 #define CARRY_WEIGHT_BIAS 1
 
 //? Item Encumbrance defines

code/__DEFINES/movespeed_modification.dm

@@ -1,7 +1,7 @@
-//! movespeed_modifier_flags
+//* movespeed_modifier_flags
 // None yet
 
-//! calculation_type
+//* calculation_type
 
 /// just use multiplicative_slowdown
 #define MOVESPEED_CALCULATION_HYPERBOLIC "hyperbolic"
@@ -20,7 +20,7 @@ DEFINE_ENUM(movespeed_modifier_calculation_type, list(
 	ENUM("Multiply", MOVESPEED_CALCULATION_MULTIPLY),
 ))
 
-//! params for add_or_update_variable_movespeed_modifier
+//* params for add_or_update_variable_movespeed_modifier
 
 /// multiplicative_slowdown
 #define MOVESPEED_PARAM_DELAY_MOD "delay"
@@ -31,13 +31,18 @@ DEFINE_ENUM(movespeed_modifier_calculation_type, list(
 /// max_tiles_per_second_boost
 #define MOVESPEED_PARAM_MAX_TILE_BOOST "max_tlies"
 
-//! Priorities - Lower is applied first
+//* Constants
+
+/// minimum movespeed
+#define MOVESPEED_ABSOLUTE_MINIMUM_TILES_PER_SECOND 0.25
+
+//* Priorities - Lower is applied first
 
 #define MOVESPEED_PRIORITY_DEFAULT 0
 #define MOVESPEED_PRIORITY_CARRY_WEIGHT 10
 
-//! Conflicts IDs
+//* Conflicts IDs
 // None yet
 
-//! IDs
+//* IDs
 // None yet

code/modules/mob/physiology.dm

@@ -22,7 +22,6 @@
 /datum/global_physiology/proc/reset()
 	carry_strength = initial(carry_strength)
 	carry_factor = initial(carry_factor)
-	carry_exponent = initial(carry_exponent)
 
 /datum/global_physiology/proc/apply(datum/physiology_modifier/modifier)
 	if(!isnull(modifier.carry_strength_add))

code/modules/movespeed/movespeed_modifier.dm

@@ -71,15 +71,23 @@ Key procs
 
 /**
   * Returns new multiplicative movespeed after modification.
+  *
+  * The minimum move delay is always world.tick_lag. Attempting to go lower will result in the excess being cut.
+  * This is so math doesn't break down when something attempts to break through the asymptote at 0 for move delay to speed.
   */
 /datum/movespeed_modifier/proc/apply_multiplicative(existing, mob/target)
-	if(!complex_calculation || (multiplicative_slowdown > 0))		// we aren't limiting how much things can slowdown.. yet.
-		return existing + multiplicative_slowdown
-	var/current_tiles = 10 / max(existing, world.tick_lag)
-	// multiplicative_slowdown is negative due to our first check
-	var/max_buff_to = max(existing + multiplicative_slowdown, 10 / absolute_max_tiles_per_second, 10 / (current_tiles + max_tiles_per_second_boost))
-	// never slow the user
-	return min(existing, max_buff_to)
+	switch(calculation_type)
+		if(MOVESPEED_CALCULATION_HYPERBOLIC)
+			return max(world.tick_lag, existing + multiplicative_slowdown)
+		if(MOVESPEED_CALCULATION_HYPERBOLIC_BOOST)
+			var/current_tiles = 10 / max(existing, world.tick_lag)
+			var/max_buff_to = max(existing + multiplicative_slowdown, 10 / absolute_max_tiles_per_second, 10 / (current_tiles + max_tiles_per_second_boost))
+			return max(world.tick_lag, min(existing, max_buff_to))
+		if(MOVESPEED_CALCULATION_MULTIPLY)
+			var/current_tiles = 10 / max(existing, world.tick_lag)
+			return max(world.tick_lag, 10 / (current_tiles * multiply_speed))
+		else
+			return existing
 
 /**
  * applies from params