add running.

create mod for player-related stuff and move hand setup from core mod to
this new mod.

add feature where, while moving, players gradually speed up up to a
certain limit. their jump height is also increased while this happens.

mods/bg_core/init.lua

@@ -2,4 +2,3 @@ local modname = minetest.get_current_modname()
 
 load_file("node")
 load_file("biome")
-load_file("hand")

mods/bg_player/init.lua

@@ -0,0 +1,2 @@
+load_file("hand")
+load_file("run")

mods/bg_player/mod.conf

@@ -0,0 +1,3 @@
+name = player
+description = blockgame player-related stuff.
+depends = core, api

mods/bg_player/run.lua

@@ -0,0 +1,52 @@
+local walk_speed = 1
+local walk_time = 2
+local speedup_time = 6
+local run_factor = 3
+local slowdown_factor = 8
+local jump_height = 1
+local jump_factor = 1.5
+
+local speed_data = {}
+
+local function handle_speed (player, delta_time)
+	speed_data[player] = speed_data[player] or {}
+	local data = speed_data[player]
+
+	-- data.start = data.start or minetest.get_gametime()
+	data.duration = (data.duration or 0) + delta_time
+
+	local control = player:get_player_control()
+
+	local moving = control.up or control.down or control.left or control.right
+	if not moving then
+		data.duration = data.duration - delta_time * (slowdown_factor + 1)
+	end
+	if data.duration < 0 then data.duration = 0 end
+
+	local duration = data.duration
+
+	local physics = player:get_physics_override()
+
+	if duration < walk_time then
+		physics.speed = walk_speed
+		physics.jump = jump_height
+	else
+		local run_time = duration - walk_time
+		local t = run_time / speedup_time
+		if t > 1 then t = 1 end
+
+		local factor = (run_factor - 1) * t + 1
+		if factor > run_factor then factor = run_factor end
+
+		physics.speed = walk_speed * factor
+		physics.jump = jump_height + (jump_height * jump_factor - 1) * t
+	end
+
+	player:set_physics_override(physics)
+end
+
+minetest.register_globalstep(function(delta_time)
+	for _, player in pairs(minetest.get_connected_players()) do
+		handle_speed(player, delta_time)
+	end
+end)