diff --git a/main.lua b/main.lua
index 4d619fd..f742719 100644
--- a/main.lua
+++ b/main.lua
@@ -132,6 +132,11 @@ local function boolean_xor(a, b)
     return true
 end
 
+local function signbyte(x)
+    if x >= 128 then x = 256 - x end
+    return x
+end
+
 local _invlog2 = 1 / log(2)
 local function log2(x) return log(x) * _invlog2 end
 
@@ -309,7 +314,7 @@ local function getxy(i, x_addr, y_addr, pageloc_addr, hipos_addr)
     end
     if hipos_addr ~= nil then
         local hipos = S(hipos_addr + i)
-        sy = sy + (hipos - 1) * 256
+        sy = sy + (signbyte(hipos) - 1) * 256
     end
 
     return sx, sy
@@ -414,9 +419,7 @@ local function handle_hammers()
         x, y = x + 8, y + 8
         local state = R(0x2A + i)
         -- skip coin effect states. not interactable; we don't care!
-        if state ~= 0
-        and state >= 0x30
-        then
+        if state ~= 0 and state >= 0x30 then
             mark_sprite(x, y, state + 1)
         else
             mark_sprite(0, 0, 0)
@@ -933,12 +936,14 @@ local function doit(dummy)
     mark_sprite(x + 8, y + 24, -powerup - 1)
 
     local vx, vy = S(0x57), S(0x9F)
-    insert(extra_input, vx)
-    insert(extra_input, vy)
+    -- i shouldn't need to do this if it's signed, but apparently...
+    insert(extra_input, signbyte(vx) * 16)
+    insert(extra_input, signbyte(vy) * 16)
 
     if cfg.time_inputs then
         for i=2,5 do
-            insert(extra_input, band(total_frames, lshift(1, i)))
+            local v = band(total_frames, lshift(1, i)) == 0 and -256 or 256
+            insert(extra_input, v)
         end
     end