diff --git a/Source/diablo.cpp b/Source/diablo.cpp
index c5a0e3304..146cec6f4 100644
--- a/Source/diablo.cpp
+++ b/Source/diablo.cpp
@@ -376,7 +376,7 @@ void diablo_parse_flags(char *args)
 			*/
 				break;
 			case 'l':
-				setlevel = 0;
+				setlevel = FALSE;
 				leveldebug = 1;
 				while (isspace(*args)) {
 					args++;
@@ -440,7 +440,7 @@ void diablo_parse_flags(char *args)
 				break;
 			case 't':
 				leveldebug = 1;
-				setlevel = 1;
+				setlevel = TRUE;
 				while (isspace(*args)) {
 					args++;
 				}
@@ -1834,7 +1834,6 @@ void LoadGameLevel(BOOL firstflag, int lvldir)
 		PlaySFX(USFX_SKING1);
 }
 // 525738: using guessed type int setseed;
-// 5CF31D: using guessed type char setlevel;
 // 679660: using guessed type char gbMaxPlayers;
 
 void game_loop(BOOL bStartup)
diff --git a/Source/gendung.cpp b/Source/gendung.cpp
index 73b089d82..35f59a5a6 100644
--- a/Source/gendung.cpp
+++ b/Source/gendung.cpp
@@ -950,6 +950,6 @@ void InitLevels()
 	if (!leveldebug) {
 		currlevel = 0;
 		leveltype = DTYPE_TOWN;
-		setlevel = 0;
+		setlevel = FALSE;
 	}
 }
diff --git a/Source/items.cpp b/Source/items.cpp
index 605dc467b..1d2f59ac6 100644
--- a/Source/items.cpp
+++ b/Source/items.cpp
@@ -510,12 +510,12 @@ void CalcPlrItemVals(int p, BOOL Loadgfx)
 	plr[p]._pILMaxDam = lmax;
 
 	if (iflgs & ISPL_INFRAVISION) {
-		plr[p]._pInfraFlag = 1;
+		plr[p]._pInfraFlag = TRUE;
 	} else {
-		plr[p]._pInfraFlag = 0;
+		plr[p]._pInfraFlag = FALSE;
 	}
 
-	plr[p]._pBlockFlag = 0;
+	plr[p]._pBlockFlag = FALSE;
 	plr[p]._pwtype = WT_MELEE;
 
 	g = 0;
@@ -552,11 +552,11 @@ void CalcPlrItemVals(int p, BOOL Loadgfx)
 	}
 
 	if (plr[p].InvBody[INVLOC_HAND_LEFT]._itype == ITYPE_SHIELD && plr[p].InvBody[INVLOC_HAND_LEFT]._iStatFlag) {
-		plr[p]._pBlockFlag = 1;
+		plr[p]._pBlockFlag = TRUE;
 		g++;
 	}
 	if (plr[p].InvBody[INVLOC_HAND_RIGHT]._itype == ITYPE_SHIELD && plr[p].InvBody[INVLOC_HAND_RIGHT]._iStatFlag) {
-		plr[p]._pBlockFlag = 1;
+		plr[p]._pBlockFlag = TRUE;
 		g++;
 	}
 
@@ -2811,21 +2811,21 @@ void PrintItemPower(char plidx, ItemStruct *x)
 		strcpy(tempstr, "damages target's armor");
 		break;
 	case IPL_FASTATTACK:
-		if (x->_iFlags & 0x20000)
+		if (x->_iFlags & ISPL_QUICKATTACK)
 			strcpy(tempstr, "quick attack");
-		if (x->_iFlags & 0x40000)
+		if (x->_iFlags & ISPL_FASTATTACK)
 			strcpy(tempstr, "fast attack");
-		if (x->_iFlags & 0x80000)
+		if (x->_iFlags & ISPL_FASTERATTACK)
 			strcpy(tempstr, "faster attack");
-		if (x->_iFlags & 0x100000)
+		if (x->_iFlags & ISPL_FASTESTATTACK)
 			strcpy(tempstr, "fastest attack");
 		break;
 	case IPL_FASTRECOVER:
-		if (x->_iFlags & 0x200000)
+		if (x->_iFlags & ISPL_FASTRECOVER)
 			strcpy(tempstr, "fast hit recovery");
-		if (x->_iFlags & 0x400000)
+		if (x->_iFlags & ISPL_FASTERRECOVER)
 			strcpy(tempstr, "faster hit recovery");
-		if (x->_iFlags & 0x800000)
+		if (x->_iFlags & ISPL_FASTESTRECOVER)
 			strcpy(tempstr, "fastest hit recovery");
 		break;
 	case IPL_FASTBLOCK:
diff --git a/Source/loadsave.cpp b/Source/loadsave.cpp
index 71472eb5b..a2b51b465 100644
--- a/Source/loadsave.cpp
+++ b/Source/loadsave.cpp
@@ -595,10 +595,10 @@ void SaveLevel()
 	pfile_write_save_file(szName, SaveBuff, tbuff - SaveBuff, dwLen);
 	mem_free_dbg(SaveBuff);
 
-	if (setlevel == 0)
-		plr[myplr]._pLvlVisited[currlevel] = 1;
+	if (!setlevel)
+		plr[myplr]._pLvlVisited[currlevel] = TRUE;
 	else
-		plr[myplr]._pSLvlVisited[setlvlnum] = 1;
+		plr[myplr]._pSLvlVisited[setlvlnum] = TRUE;
 }
 
 void LoadLevel()
diff --git a/Source/missiles.cpp b/Source/missiles.cpp
index 9b6c695cc..940ac3077 100644
--- a/Source/missiles.cpp
+++ b/Source/missiles.cpp
@@ -1240,7 +1240,7 @@ void AddArrow(int mi, int sx, int sy, int dx, int dy, int midir, char mienemy, i
 	}
 	if (!mienemy) {
 		av = 32;
-		if (plr[id]._pIFlags & 4) {
+		if (plr[id]._pIFlags & ISPL_RNDARROWVEL) {
 			av = random(64, 32) + 16;
 		}
 		if (plr[id]._pClass == PC_ROGUE)
@@ -1299,7 +1299,7 @@ void AddRndTeleport(int mi, int sx, int sy, int dx, int dy, int midir, char mien
 
 	missile[mi]._miVar1 = 0;
 	missile[mi]._mirange = 2;
-	if (setlevel == 0 || setlvlnum != SL_VILEBETRAYER) {
+	if (!setlevel || setlvlnum != SL_VILEBETRAYER) {
 		missile[mi]._mix = sx + r1;
 		missile[mi]._miy = sy + r2;
 		if (!mienemy)
diff --git a/Source/msg.cpp b/Source/msg.cpp
index 5bc81520c..4b3cd2fa8 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -452,7 +452,7 @@ void DeltaSaveLevel()
 			if (i != myplr)
 				plr[i]._pGFXLoad = 0;
 		}
-		plr[myplr]._pLvlVisited[currlevel] = 1;
+		plr[myplr]._pLvlVisited[currlevel] = TRUE;
 		delta_leave_sync(currlevel);
 	}
 }
@@ -2337,7 +2337,7 @@ DWORD On_PLAYER_JOINLEVEL(TCmd *pCmd, int pnum)
 	if (gbBufferMsgs == 1)
 		msg_send_packet(pnum, p, sizeof(*p));
 	else {
-		plr[pnum]._pLvlChanging = 0;
+		plr[pnum]._pLvlChanging = FALSE;
 		if (plr[pnum]._pName[0] && !plr[pnum].plractive) {
 			plr[pnum].plractive = TRUE;
 			gbActivePlayers++;
diff --git a/Source/multi.cpp b/Source/multi.cpp
index 3033ce1be..844e54f3a 100644
--- a/Source/multi.cpp
+++ b/Source/multi.cpp
@@ -772,7 +772,7 @@ void SetupLocalCoords()
 	if (!leveldebug || gbMaxPlayers > 1) {
 		currlevel = 0;
 		leveltype = DTYPE_TOWN;
-		setlevel = 0;
+		setlevel = FALSE;
 	}
 	x = 75;
 	y = 68;
@@ -791,7 +791,7 @@ void SetupLocalCoords()
 	plr[myplr]._ptargx = x;
 	plr[myplr]._ptargy = y;
 	plr[myplr].plrlevel = currlevel;
-	plr[myplr]._pLvlChanging = 1;
+	plr[myplr]._pLvlChanging = TRUE;
 	plr[myplr].pLvlLoad = 0;
 	plr[myplr]._pmode = PM_NEWLVL;
 	plr[myplr].destAction = ACTION_NONE;
diff --git a/Source/objects.cpp b/Source/objects.cpp
index c57efcba8..4f84bad9c 100644
--- a/Source/objects.cpp
+++ b/Source/objects.cpp
@@ -2462,7 +2462,7 @@ void OperateBook(int pnum, int i)
 	}
 	object[i]._oAnimFrame++;
 	object[i]._oSelFlag = 0;
-	if (setlevel == 0)
+	if (!setlevel)
 		return;
 
 	if (setlvlnum == SL_BONECHAMB) {
@@ -2485,7 +2485,7 @@ void OperateBook(int pnum, int i)
 		    0,
 		    0);
 	}
-	if (setlevel != 0 && setlvlnum == SL_VILEBETRAYER) {
+	if (setlevel && setlvlnum == SL_VILEBETRAYER) {
 		ObjChangeMapResync(
 		    object[i]._oVar1,
 		    object[i]._oVar2,
diff --git a/Source/player.cpp b/Source/player.cpp
index 0d14040b1..9a1e92d32 100644
--- a/Source/player.cpp
+++ b/Source/player.cpp
@@ -590,7 +590,7 @@ void CreatePlayer(int pnum, char c)
 	plr[pnum]._pFireResist = 0;
 	plr[pnum]._pLghtResist = 0;
 	plr[pnum]._pLightRad = 10;
-	plr[pnum]._pInfraFlag = 0;
+	plr[pnum]._pInfraFlag = FALSE;
 
 	if (c == PC_WARRIOR) {
 		plr[pnum]._pAblSpells = (__int64)1 << (SPL_REPAIR - 1);
@@ -631,14 +631,14 @@ void CreatePlayer(int pnum, char c)
 	}
 
 	for (i = 0; i < NUMLEVELS; i++) {
-		plr[pnum]._pLvlVisited[i] = 0;
+		plr[pnum]._pLvlVisited[i] = FALSE;
 	}
 
 	for (i = 0; i < 10; i++) {
-		plr[pnum]._pSLvlVisited[i] = 0;
+		plr[pnum]._pSLvlVisited[i] = FALSE;
 	}
 
-	plr[pnum]._pLvlChanging = 0;
+	plr[pnum]._pLvlChanging = FALSE;
 	plr[pnum].pTownWarps = 0;
 	plr[pnum].pLvlLoad = 0;
 	plr[pnum].pBattleNet = 0;
@@ -1960,12 +1960,12 @@ void InitLevelChange(int pnum)
 	if (pnum == myplr) {
 		dPlayer[plr[myplr].WorldX][plr[myplr].WorldY] = myplr + 1;
 	} else {
-		plr[pnum]._pLvlVisited[plr[pnum].plrlevel] = 1;
+		plr[pnum]._pLvlVisited[plr[pnum].plrlevel] = TRUE;
 	}
 
 	ClrPlrPath(pnum);
 	plr[pnum].destAction = ACTION_NONE;
-	plr[pnum]._pLvlChanging = 1;
+	plr[pnum]._pLvlChanging = TRUE;
 
 	if (pnum == myplr) {
 		plr[pnum].pLvlLoad = 10;
diff --git a/Source/portal.cpp b/Source/portal.cpp
index dfffa8872..296fea10f 100644
--- a/Source/portal.cpp
+++ b/Source/portal.cpp
@@ -121,19 +121,19 @@ void SetCurrentPortal(int p)
 void GetPortalLevel()
 {
 	if (currlevel) {
-		setlevel = 0;
+		setlevel = FALSE;
 		currlevel = 0;
 		plr[myplr].plrlevel = 0;
 		leveltype = DTYPE_TOWN;
 	} else {
 		if (portal[portalindex].setlvl) {
-			setlevel = 1;
+			setlevel = TRUE;
 			setlvlnum = portal[portalindex].level;
 			currlevel = portal[portalindex].level;
 			plr[myplr].plrlevel = setlvlnum;
 			leveltype = portal[portalindex].ltype;
 		} else {
-			setlevel = 0;
+			setlevel = FALSE;
 			currlevel = portal[portalindex].level;
 			plr[myplr].plrlevel = currlevel;
 			leveltype = portal[portalindex].ltype;
diff --git a/Source/spells.cpp b/Source/spells.cpp
index 6eac5afea..81bd6de1b 100644
--- a/Source/spells.cpp
+++ b/Source/spells.cpp
@@ -167,7 +167,7 @@ void DoResurrect(int pnum, int rid)
 
 		ClrPlrPath(rid);
 		plr[rid].destAction = ACTION_NONE;
-		plr[rid]._pInvincible = 0;
+		plr[rid]._pInvincible = FALSE;
 		PlacePlayer(rid);
 
 		hp = 640;
diff --git a/Source/trigs.cpp b/Source/trigs.cpp
index 6928d668d..fa2249976 100644
--- a/Source/trigs.cpp
+++ b/Source/trigs.cpp
@@ -695,7 +695,6 @@ void CheckTrigForce()
 		ClearPanel();
 	}
 }
-// 5CF31D: using guessed type char setlevel;
 
 void CheckTriggers()
 {
diff --git a/structs.h b/structs.h
index dd100d914..494860fba 100644
--- a/structs.h
+++ b/structs.h
@@ -224,10 +224,10 @@ typedef struct PlayerStruct {
 	int _pSplHotKey[4];
 	char _pSplTHotKey[4];
 	int _pwtype;
-	unsigned char _pBlockFlag;
-	unsigned char _pInvincible;
+	BOOLEAN _pBlockFlag;
+	BOOLEAN _pInvincible;
 	char _pLightRad;
-	unsigned char _pLvlChanging;
+	BOOLEAN _pLvlChanging;
 	char _pName[PLR_NAME_LEN];
 	// plr_class enum value.
 	// TODO: this could very well be `enum plr_class _pClass`
@@ -267,7 +267,7 @@ typedef struct PlayerStruct {
 	char _pFireResist;
 	char _pLghtResist;
 	int _pGold;
-	int _pInfraFlag;
+	BOOL _pInfraFlag;
 	int _pVar1;
 	int _pVar2;
 	int _pVar3;
@@ -276,8 +276,8 @@ typedef struct PlayerStruct {
 	int _pVar6;
 	int _pVar7;
 	int _pVar8;
-	unsigned char _pLvlVisited[NUMLEVELS];
-	unsigned char _pSLvlVisited[NUMLEVELS]; // only 10 used
+	BOOLEAN _pLvlVisited[NUMLEVELS];
+	BOOLEAN _pSLvlVisited[NUMLEVELS]; // only 10 used
 	int _pGFXLoad;
 	unsigned char *_pNAnim[8];
 	int _pNFrames;