diff --git a/src/main.lua b/src/main.lua
index 5462775..2fcd395 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -6,6 +6,14 @@ import 'CoreLibs/object.lua'
 import 'CoreLibs/ui.lua'
 import 'utils.lua'
 
+--- @alias Position { x: number, y: number }
+
+--- @alias Base { x: number, y: number }
+
+--- @alias Runner { x: number, y: number, nextBase: Base, prevBase: Base, forcedTo: Base }
+
+--- @alias Fielder { onArrive: fun() | nil, x: number | nil, y: number | nil, targetX: number | nil, targetY: number | nil }
+
 local gfx = playdate.graphics
 playdate.display.setRefreshRate(50)
 gfx.setBackgroundColor(gfx.kColorWhite)
@@ -38,9 +46,10 @@ local batBaseX, batBaseY = centerX - 34, 215
 
 local batLength = 45
 
+local tagDistance = 20
+
 local ballY = ballStartY
 local ballX = 200
-local ballVelX, ballVelY = 0, 0
 local ballSize = 6
 
 local batTipX = 0
@@ -59,6 +68,7 @@ local hitMult = 10
 
 local deltaTime = 0
 
+---@type table<string, Base>
 local bases = {
     first = { x = screenW * 0.93, y = screenH * 0.52 },
     second = { x = screenW * 0.47, y = screenH * 0.19 },
@@ -66,12 +76,20 @@ local bases = {
     home = { x = screenW * 0.474, y = screenH * 0.79 }
 }
 
+---@type table<Base, Base>
+local nextBaseMap = {
+    [bases.first] = bases.second,
+    [bases.second] = bases.third,
+    [bases.third] = bases.home
+}
+
 local fielderSpeed = 40
+
+---@type table<string, Fielder>
 local fielders = {
     first = {
         x = nil,
         y = nil,
-        covering = nil -- TODO?
     },
     second = {},
     shortstop = {},
@@ -81,6 +99,7 @@ local fielders = {
     center = {},
     right = {}
 }
+
 function resetFielderPositions()
     fielders.first.x = screenW - 65
     fielders.first.y = screenH * 0.48
@@ -110,15 +129,24 @@ resetFielderPositions()
 
 local playerStartingX = bases.home.x - 40
 local playerStartingY = bases.home.y - 3
-local player = {
-    x = playerStartingX,
-    y = playerStartingY,
-    nextBase = nil,
-    prevBase = nil,
-}
 
+--- @type table<Runner, Runner>
 local runners = { }
 
+---@return Runner
+function newRunner()
+    local new = {
+        x = playerStartingX,
+        y = playerStartingY,
+        nextBase = nil,
+        prevBase = nil,
+    }
+    runners[#runners + 1] = new
+    return new
+end
+
+local batter = newRunner()
+
 function throwBall(destX, destY, easingFunc, flyTimeMs)
     if not flyTimeMs then
         flyTimeMs = distanceBetween(ballX, ballY, destX, destY) * 5
@@ -131,8 +159,6 @@ end
 function pitch()
     pitchAnimator:reset()
     resetFielderPositions()
-    ballVelX = 0
-    ballVelY = 0
     ballX = 200
     currentMode = MODES.batting
 
@@ -140,9 +166,10 @@ function pitch()
     backgroundPan.x = 0
 
     -- TODO: Add new runners, instead
-    runners = {}
-    player.x = playerStartingX
-    player.y = playerStartingY
+    --runners = {}
+    --batter.x = playerStartingX
+    --batter.y = playerStartingY
+    batter = newRunner()
 end
 
 function playdate.AButtonDown()
@@ -169,6 +196,34 @@ local pitchClockSec = 99
 local elapsedTime = 0
 local crankChange
 
+local baseHitbox = 13
+--- Returns the base being touched by the runner at (x,y), or nil, if no base is being touched
+function isTouchingBase(x, y)
+    for _,base in pairs(bases) do
+        if distanceBetween(x, y, base.x, base.y) < baseHitbox then
+            return base
+        end
+    end
+
+    return nil
+end
+
+local ballCatchHitbox = 3
+function isTouchingBall(x, y)
+    local ballDistance = distanceBetween(x, y, ballX, ballY)
+    -- print("ballDistance:")
+    -- print(ballDistance)
+    return ballDistance < ballCatchHitbox
+end
+
+function updateForcedTos()
+end
+
+function outRunner(runnerIndex)
+    table.remove(runners, runnerIndex)
+    updateForcedTos()
+end
+
 function updateInfield()
     if ballDestX == nil or ballDestY == nil then
         return
@@ -189,66 +244,93 @@ function updateInfield()
                 fielder.targetY = nil
             end
         end
-    end
-end
 
-function updateRunners()
-    local runnerSpeed = 20
-    for i,runner in pairs(runners) do
-        if runner.nextBase then
-            local nb = runner.nextBase
-            local x, y, distance = normalizeVector(runner.x, runner.y, nb.x, nb.y)
-            runner.hasArrived = distance <= 1
-
-            if runner.hasArrived then
-                -- if runner.onArrive then
-                --     runner.onArrive()
-                -- end
-                runner.targetX = nil
-                runner.targetY = nil
-            else
-                local mult = 1
-                if crankChange < 0 then
-                    mult = -1
+        if isTouchingBall(fielder.x, fielder.y) then
+            local touchedBase = isTouchingBase(fielder.x, fielder.y)
+            for i,runner in pairs(runners) do
+                local runnerOnBase = isTouchingBase(runner.x, runner.y)
+                if touchedBase and runner.forcedTo == touchedBase and touchedBase ~= runnerOnBase then
+                    outRunner(i)
+                elseif not runnerOnBase then
+                    local fielderDistance = distanceBetween(runner.x, runner.y, fielder.x, fielder.y)
+                    if fielderDistance < tagDistance then
+                        outRunner(i)
+                    end
                 end
-                mult = (mult * runnerSpeed * deltaTime) + (crankChange / 20)
-                runner.x -= x * mult
-                runner.y -= y * mult
             end
         end
     end
 end
 
-function getNearestFielder(x, y)
-    local nearestFielder, nearestDistance = nil, nil
-    for _, fielder in pairs(fielders) do
-        if nearestFielder == nil then
-            nearestFielder = fielder
-            nearestDistance = distanceBetween(fielder.x, fielder.y, x, y)
+--- Returns the nearest base, as well as the distance from that base
+---@generic T : {x: number, y: number}
+---@param array T[]
+---@param x: number
+---@param y: number
+---@return T,number
+function getNearestOf(array, x, y)
+    local nearest, nearestDistance = nil, nil
+    for _, element in pairs(array) do
+        if nearest == nil then
+            nearest = element
+            nearestDistance = distanceBetween(element.x, element.y, x, y)
         else
-            local distance = distanceBetween(fielder.x, fielder.y, x, y)
+            local distance = distanceBetween(element.x, element.y, x, y)
             if distance < nearestDistance then
-                nearestFielder = fielder
+                nearest = element
                 nearestDistance = distance
             end
         end
     end
 
-    return nearestFielder
+    return nearest, nearestDistance
 end
 
+function updateRunners()
+    local runnerSpeed = 20
+    local nonPlayerRunners = filter(runners, function (runner)
+        return runner ~= batter
+    end)
+    for _,runner in pairs(nonPlayerRunners) do
+        local nearestBase, nearestBaseDistance = getNearestOf(bases, runner.x, runner.y)
+        if runner.nextBase then
+            local nb = runner.nextBase
+            local x, y, distance = normalizeVector(runner.x, runner.y, nb.x, nb.y)
+
+            if distance > 1 then
+                local mult = 1
+                if crankChange < 0 then
+                    mult = -1
+                end
+                -- TODO: Drift toward nearest base?
+                local autoRun = nearestBaseDistance > 5 and mult * runnerSpeed * deltaTime or 0
+                mult = autoRun + (crankChange / 20)
+                runner.x -= x * mult
+            runner.y -= y * mult
+            else
+                runner.nextBase = nextBaseMap[runner.nextBase]
+                runner.forcedTo = nil
+            end
+        end
+    end
+end
+
+---@return boolean
 function ballIsBeingThrown()
     return false
 end
 
+---@return boolean
 function throwArrivedBeforeRunner()
     return false
 end
 
+---@return Base[]
 function getForcedOutTargets()
     return { bases.first }
 end
 
+---@return number,number
 function getNextThrowTarget()
     local targets = getForcedOutTargets()
     return targets[1].x, targets[1].y
@@ -273,7 +355,7 @@ function updateGameState()
         ballSize = 6
     end
 
-    batAngle = math.rad(playdate.getCrankPosition() + 90)
+    local batAngle = math.rad(playdate.getCrankPosition() + 90)
     batTipX = batBaseX + (batLength * math.sin(batAngle))
     batTipY = batBaseY + (batLength * math.cos(batAngle))
 
@@ -283,9 +365,9 @@ function updateGameState()
         currentMode = MODES.running
         ballAngle = batAngle + math.rad(90)
 
-        mult = math.abs(acceleratedChange / 15)
-        ballVelX = mult * 10 * math.sin(ballAngle)
-        ballVelY = mult * 5 * math.cos(ballAngle)
+        local mult = math.abs(acceleratedChange / 15)
+        local ballVelX = mult * 10 * math.sin(ballAngle)
+        local ballVelY = mult * 5 * math.cos(ballAngle)
         if ballVelY > 0 then
             ballVelX = ballVelX * -1
             ballVelY = ballVelY * -1
@@ -293,7 +375,7 @@ function updateGameState()
         ballDestX = ballX + (ballVelX * hitMult)
         ballDestY = ballY + (ballVelY * hitMult)
         throwBall(ballDestX, ballDestY, playdate.easingFunctions.outQuint, 2000)
-        local chasingFielder = getNearestFielder(ballDestX, ballDestY)
+        local chasingFielder = getNearestOf(fielders, ballDestX, ballDestY)
         chasingFielder.targetX = ballDestX
         chasingFielder.targetY = ballDestY
         chasingFielder.onArrive = function()
@@ -303,20 +385,27 @@ function updateGameState()
         end
         fielders.first.targetX = bases.first.x
         fielders.first.targetY = bases.first.y
-        player.nextBase = bases.first
-        runners[#runners+1] = player
+        batter.nextBase = bases.first
+        batter.forcedTo = bases.first
+        batter = nil -- Demote batter to a mere runner
     end
 
     if currentMode == MODES.running then
         updateRunners()
         updateInfield()
     end
+end
+
+function playdate.update()
+    updateGameState()
+    playdate.graphics.animation.blinker.updateAll()
 
     -- TODO: Show baserunning minimap when panning?
     local ballBuffer = 5
     if ballY < ballBuffer then
         backgroundPan.y = math.max(ballBuffer, -1 * (ballY - ballBuffer))
-    else backgroundPan.y = 0
+    else
+        backgroundPan.y = 0
     end
     if ballX < ballBuffer then
         backgroundPan.x = math.max(-400, -1 * (ballX - ballBuffer))
@@ -327,11 +416,6 @@ function updateGameState()
     if ballX > 0 and ballX < (screenW - ballBuffer) then
         backgroundPan.x = 0
     end
-end
-
-function playdate.update()
-    updateGameState()
-    playdate.graphics.animation.blinker.updateAll()
 
     gfx.clear()
     grassBackground:draw(backgroundPan.x - 400, backgroundPan.y - 240)
@@ -358,13 +442,12 @@ function playdate.update()
     end
 
     -- TODO? Change blip speed depending on runner speed?
-    playerImageBlipper:draw(
-            currentMode ~= MODES.running,
-        player.x + backgroundPan.x,
-        player.y + backgroundPan.y
-    )
+    for _,runner in pairs(runners) do
+        playerImageBlipper:draw(
+                false,
+                runner.x + backgroundPan.x,
+                runner.y + backgroundPan.y
+        )
+    end
 
-    -- for i,runner in pairs(runners) do
-    --     playerImage:draw(runner.x, runner.y)
-    -- end
 end
diff --git a/src/utils.lua b/src/utils.lua
index 86820e8..b7069c9 100644
--- a/src/utils.lua
+++ b/src/utils.lua
@@ -2,11 +2,40 @@ import 'CoreLibs/animation.lua'
 import 'CoreLibs/graphics.lua'
 
 --- Returns the normalized vector as two values, plus the distance between the given points.
+---@return number, number, number
 function normalizeVector(x1, y1, x2, y2)
     local distance, a, b = distanceBetween(x1, y1, x2, y2)
     return a / distance, b / distance, distance
 end
 
+---@generic T
+---@param array T[]
+---@param condition fun(T): boolean
+---@return T[]
+function filter(array, condition)
+    local newArray = {}
+    for _,element in pairs(array) do
+        if condition(element) then
+            newArray[#newArray + 1] = element
+        end
+    end
+    return newArray
+end
+
+---@generic TIn
+---@generic TOut
+---@param array TIn[]
+---@param condition fun(TIn): TOut
+---@return TOut[]
+function map(array, mapper)
+    local newArray = {}
+    for _,element in pairs(array) do
+        newArray[#newArray + 1] = mapper(element)
+    end
+    return newArray
+end
+
+---@return number, number, number
 function distanceBetween(x1, y1, x2, y2)
     local a = x1 - x2
     local b = y1 - y2