diff --git a/luprex/cpp/core/animqueue.cpp b/luprex/cpp/core/animqueue.cpp
index 27701058..10c7bb42 100644
--- a/luprex/cpp/core/animqueue.cpp
+++ b/luprex/cpp/core/animqueue.cpp
@@ -21,7 +21,7 @@ static const char *vtname(AnimValueType vt) {
 }
 
 
-uint64_t hash_encstep(uint64_t prev, std::string_view s) {
+static uint64_t hash_encstep(uint64_t prev, std::string_view s) {
     return util::hash_string(util::HashValue(123, prev), s).first;
 }
 
@@ -420,102 +420,114 @@ void AnimCoreState::decode(std::string_view s) {
 }
 
 int AnimQueue::get_size_limit() const {
+    if (encqueue_ == nullptr) return 0;
     StreamBuffer sb(*encqueue_);
     return sb.read_uint8();
 }
 
 int AnimQueue::get_actual_size() const {
+    if (encqueue_ == nullptr) return 0;
     StreamBuffer sb(*encqueue_);
     sb.read_bytes(1);
     return sb.read_uint8();
 }
 
 uint64_t AnimQueue::get_final_hash() const {
+    if (encqueue_ == nullptr) return 0;
     StreamBuffer sb(*encqueue_);
     sb.read_bytes(2);
     return sb.read_uint64();
 }
 
 std::string_view AnimQueue::get_final_encstep() const {
+    if (encqueue_ == nullptr) return std::string_view();
     StreamBuffer sb(*encqueue_);
     sb.read_bytes(10);
     return sb.read_string_view();
 }
 
-void AnimQueue::update_encqueue(int limit, bool add, std::string_view add_enc, bool keepold) {
-    // Make sure the size limit is reasonable.
-    assert((limit >= 2) && (limit <= 250));
+AnimQueue::QueueRange AnimQueue::get_range(int lo, int hi) {
+    // Clamp lo and hi to the valid range (0 to actual_size).
+    //
+    int actual_size = get_actual_size();
+    if (lo < 0) lo = 0;
+    if (hi > actual_size) hi = actual_size;
 
-    // You must either add a new step or retain an old step.  The queue can't be empty.
-    assert(keepold || add);
+    // Abort early if the range is empty.  This avoids several edge cases.
+    //
+    if (lo >= hi) return QueueRange(0, std::string_view());
 
-    // Find out how many old steps we'll be retaining, ignoring the size limit.
-    int nretain = 0;
-    if (keepold) nretain = get_actual_size();
-    
-    // If retaining all steps would overflow the size limit, retain fewer.
-    int retain_limit = limit;
-    if (add) retain_limit -= 1;
-    if (nretain > retain_limit) nretain = retain_limit;
-
-    // Calculate the new size of the queue.
-    int new_size = add ? (nretain + 1) : nretain;
-    
-    // If we're retaining steps, extract them from the old queue.
-    std::string_view retain;
-    if (nretain > 0) {
-        std::string_view oldqueue(*encqueue_);
-        StreamBuffer sb(oldqueue);
-        sb.read_bytes(2); // Skip over the header.
-        int pos1 = sb.total_reads();
-        for (int i = 0; i < nretain; i++) {
-            sb.read_uint64();
-            sb.read_string_view();
-        }
-        int pos2 = sb.total_reads();
-        retain = oldqueue.substr(pos1, pos2 - pos1);
+    // Get the entries.
+    //
+    std::string_view queueview(*encqueue_);
+    StreamBuffer sb(queueview);
+    sb.read_bytes(2); // Skip over the header.
+    for (int i = 0; i < lo; i++) {
+        sb.read_uint64();
+        sb.read_string_view();
     }
-
-    // If we're adding a step, calculate its hash.
-    uint64_t add_hash = 0;
-    if (add) {
-        uint64_t prev_hash = 0;
-        if (nretain > 0) prev_hash = get_final_hash();
-        add_hash = hash_encstep(prev_hash, add_enc);
+    int pos1 = sb.total_reads();
+    for (int i = lo; i < hi; i++) {
+        sb.read_uint64();
+        sb.read_string_view();
     }
+    int pos2 = sb.total_reads();
+    return QueueRange(hi-lo, queueview.substr(pos1, pos2 - pos1));
+}
 
-    // Finally, encode everything into a binary blob.
+uint64_t AnimQueue::hash_encstep(const QueueRange &prev, std::string_view s) {
+    uint64_t prev_hash = 0;
+    if (prev.size > 0) {
+        StreamBuffer retsb(prev.entries);
+        prev_hash = retsb.read_uint64();
+    }
+    return ::hash_encstep(prev_hash, s);
+}
+
+void AnimQueue::update_encqueue(int limit, bool add, std::string_view add_enc, int keeplo, int keephi) {
+    // Get the retained entries.
+    QueueRange keeprange = get_range(keeplo, keephi);
+    
+    // Encode everything into a binary blob.
     StreamBuffer result;
     result.write_uint8(limit);
-    result.write_uint8(new_size);
+    result.write_uint8(keeprange.size + (add ? 1:0));
     if (add) {
+        uint64_t add_hash = hash_encstep(keeprange, add_enc);
         result.write_uint64(add_hash);
         result.write_string(add_enc);
     }
-    result.write_bytes(retain);
+    result.write_bytes(keeprange.entries);
 
     // Replace the shared string.
     encqueue_ = std::make_shared<std::string>(result.view());
 }
 
 AnimQueue::AnimQueue() {
-    update_encqueue(10, true, AnimState().encode(), false);
+    update_encqueue(10, true, AnimState().encode(), 0, 0);
 }
 
 void AnimQueue::clear(const AnimState &state) {
-    update_encqueue(get_size_limit(), true, state.encode(), false);
+    update_encqueue(get_size_limit(), true, state.encode(), 0, 0);
 }
 
 void AnimQueue::clear() {
-    update_encqueue(get_size_limit(), true, AnimState().encode(), false);
+    update_encqueue(get_size_limit(), true, AnimState().encode(), 0, 0);
 }
 
 void AnimQueue::set_limit(int limit) {
-    update_encqueue(limit, false, "", true);
+    assert((limit >= 2) && (limit <= 250));
+    update_encqueue(limit, false, std::string_view(), 0, limit);
 }
 
 void AnimQueue::add(const AnimState &state) {
-    update_encqueue(get_size_limit(), true, state.encode(), true);
+    int limit = get_size_limit();
+    update_encqueue(limit, true, state.encode(), 0, limit - 1);
+}
+
+void AnimQueue::replace(const AnimState &state) {
+    int limit = get_size_limit();
+    update_encqueue(limit, true, state.encode(), 1, limit);
 }
 
 void AnimQueue::serialize(StreamBuffer *sb) const {
diff --git a/luprex/cpp/core/animqueue.hpp b/luprex/cpp/core/animqueue.hpp
index 9d4add91..14434337 100644
--- a/luprex/cpp/core/animqueue.hpp
+++ b/luprex/cpp/core/animqueue.hpp
@@ -268,6 +268,13 @@ public:
     //
     void add(const AnimState &state);
 
+    // Replace the most recent animation step.
+    //
+    // Note: replace does not automatically compose the step with the previous
+    // step, you have to do that yourself.
+    //
+    void replace(const AnimState &state);
+
     // Serialize or deserialize to a StreamBuffer
     //
     void serialize(StreamBuffer *sb) const;
@@ -316,14 +323,41 @@ public:
     util::SharedStdString get_encoded_queue() const { return encqueue_; }
 
 private:
-    // Update the encoded queue.
-    //
-    // You must specify the new size limit.
-    // You may optionally specify an encstep to add.
-    // If keepold, then old steps will be retained up to the size limit.
-    //
-    void update_encqueue(int limit, bool add, std::string_view add_enc, bool keepold);
+    struct QueueRange {
+        int size;
+        std::string_view entries;
+        QueueRange(int sz, std::string_view ent) : size(sz), entries(ent) {}
+    };
 
+    // Get a range of entries from the queue.
+    //
+    // You must specify a range (lo-hi) of steps.  In this numbering, 0 is the
+    // most recent entry in the queue.  The indices lo and hi are automatically
+    // clamped to the valid range (0 to actual_size).  If lo >= hi, then an
+    // empty range is returned.
+    //
+    QueueRange get_range(int lo, int hi);
+
+    // Hash a new step given the range of steps that precede it.
+    //
+    static uint64_t hash_encstep(const QueueRange &prev, std::string_view step);
+
+    // Update the animation queue.
+    //
+    // The range (keeplo to keephi) specifies which old steps should be
+    // retained.  The numbers keephi and keeplo are automatically clamped
+    // so that they lie inside the actual size of the queue.
+    //
+    // If add is true, then an additional step is added to the queue.
+    // The hash of the new step is calculated automatically.
+    //
+    // There is no enforcement that you respected the size limit that you
+    // specified.  For example, you could say "keep 0-5, and add 1."  That
+    // would make 6 entries in the queue.  It is up to the caller to respect
+    // the size limit.  The value passed in is just for reporting.
+    // 
+    void update_encqueue(int limit, bool add, std::string_view add_enc, int keeplo, int keephi);
+    
     // Read values from the header of the encqueue.
     //
     int get_size_limit() const;
diff --git a/luprex/cpp/core/world-accessor.cpp b/luprex/cpp/core/world-accessor.cpp
index 89e51a31..8fba0bda 100644
--- a/luprex/cpp/core/world-accessor.cpp
+++ b/luprex/cpp/core/world-accessor.cpp
@@ -45,85 +45,85 @@ LuaDefine(tangible_animdebug, "tan",
     return LS.result();
 }
 
-LuaDefine(tangible_animstate, "tan",
-    "|Return the animation state variables of the tangible as a table."
+LuaDefine(tangible_animfinal, "tan",
+    "|Return the final step in the animation queue."
     "|"
-    "|The animation system stores 'animation state variables. "
-    "|There are several builtin animation state variables.  The"
-    "|following is a list, along with some example values that"
-    "|might be used if the object were a pirate treasure chest."
+    "|The animation queue stores animation steps.  This function returns"
+    "|the final animation step.  An animation step consists of key-value"
+    "|pairs.  Some of those key-value pairs describe the last thing that"
+    "|happened to the tangible.  Others describe the final resting place"
+    "|of the tangible."
     "|"
+    "|For example, if the tangible were a pirate chest, the key-value"
+    "|pairs might be:"
+    "|"
+    "|  action='open'            # last thing the chest did"
     "|  xyz={1,2,3}              # xyz coordinate"
     "|  plane='earth'            # plane where the chest is located"
     "|  facing=0                 # rotation of the chest"
-    "|  bp='BP_piratechest'      # name of an unreal blueprint"
-    "|  model='SM_piratechest'   # name of an unreal mesh"
-    "|"
-    "|There can also be user-defined animation state variables."
-    "|For example, for a pirate chest, you might want to add two"
-    "|more state variables:"
-    "|"
     "|  open=true                # chest can be open or closed"
     "|  fullness=0.8             # how big the heap of coins is"
     "|"
-    "|All state variables must be one of four types: number, string,"
-    "|boolean, or coordinate.  All state variables must have simple"
-    "|identifiers for names."
-    "|"
-    "|Animation state variables are updated when you use"
-    "|tangible.animate to create an animation record.  For example,"
-    "|suppose your character is initialized at xyz={1,1,1}.  Then"
-    "|he walks to xyz={2,2,2}, then he walks to xyz={3,3,3}."
-    "|The animation queue now contains three animation steps:"
-    "|"
-    "|Animation Queue:"
-    "|   Step 1: action:initialize xyz={1,1,1} ..."
-    "|   Step 2: action:walkto     xyz={2,2,2} ..."
-    "|   Step 3: action:walkto     xyz={3,3,3} ..."
-    "|"
-    "|Notice that the state variable xyz is stored three times, once"
-    "|in each animation step.  All animation state variables are stored"
-    "|in every animation step.  When you use tangible.animstate to fetch"
-    "|the current value of the animation state variables, you're"
-    "|actually fetching the state variables from the last step in"
-    "|the animation queue."
-    "|"
-    "|You can use this function, tangible.animstate, to view the"
-    "|current set of state variables.  You can use tangible.animinit"
-    "|to reconfigure the set of user-defined state variables.  You"
-    "|can use tangible.animate to create animation steps, which can"
-    "|alter any of the state variables."
+    "|See doc(tangible.animinit) for more information about animation queues."
     "|") {
     LuaArg tanobj;
     LuaRet result;
     LuaDefStack LS(L, tanobj, result);
     World *w = World::fetch_global_pointer(L);
     Tangible *tan = w->tangible_get(LS, tanobj, false);
-    AnimState state = tan->anim_queue_.get_final_persistent();
+    AnimState state = tan->anim_queue_.get_final_everything();
     state.to_lua(LS, result, true);
     return LS.result();
 }
 
 LuaDefine(tangible_animinit, "tan,config",
-    "|Reinitialize the animation queue."
+    "|Reinitialize the animation queue and specify persistent state."
     "|"
-    "|The animation queue stores certain animation state variables."
-    "|See doc(tangible.animstate) for more information about animation"
-    "|state variables."
+    "|Every tangible has an animation queue.  The queue consists of a"
+    "|sequence of animation steps.  Each step consists of a list of"
+    "|key-value pairs.  For example, if you want a human person to jump"
+    "|three feet in the air, you might find this animation step in the"
+    "|animation queue:"
+    "|"
+    "|  action='jump'       - the name of the animation to perform"
+    "|  height=3.0          - the height to which you want him to jump"
+    "|  xyz={1,2,3}         - person's xyz coordinate during the jump"
+    "|  plane=earth         - plane where the jump takes place"
+    "|"
+    "|Some of those key-value pairs are 'persistent'.  For example, xyz is"
+    "|persistent.  That means that the player must always have an xyz"
+    "|coordinate.  Every single animation step in the queue must"
+    "|contain a value for xyz.  Likewise, 'plane' is a persistent variable."
+    "|The player must always be on some plane or another."
+    "|"
+    "|When you add an animation step to the animation queue, you do not have"
+    "|to always specify xyz and plane.  For example, you can legally say:"
+    "|"
+    "|  tangible.animate(a, nil, {action='jump', height=3.0}))"
+    "|"
+    "|This adds a step to the animation queue.  That step contains"
+    "|xyz and plane, even though we didn't specify xyz and plane in"
+    "|the 'animate' command above.  The values for xyz and plane will be"
+    "|copied over from the previous animation step.  In this way, those values"
+    "|get persisted: they stay the same unless you change them in"
+    "|the 'animate' command."
+    "|"
+    "|There are five hardwired persistent variables: plane,xyz,facing,bp,model."
+    "|These five variables are persistent no matter what.  This function,"
+    "|tangible.animinit, optionally allows you to create more persistent"
+    "|variables.  For example, let's say you have a pirate chest.  You might"
+    "|want to add two persistent variables in addition to the usual set:"
+    "|"
+    "|    open=true         - whether the chest is open or closed"
+    "|    heapsize=0.8      - the size of the heap of coins"
+    "|"
+    "|Making a variable persistent means that it will always have a value"
+    "|no matter what you do."
     "|"
     "|This function, tangible.animinit, is used to reconfigure the set of"
-    "|user-defined state variables.  The config table that you pass in must"
-    "|be key-value pairs.  Keys must be simple identifiers.  Values can be"
-    "|numbers, strings, booleans, or coordinates."
-    "|"
-    "|After tangible.animinit, the tangible's animation state variables will"
-    "|consist of the user-defined variables listed in the config table,"
-    "|plus all the builtin animation state variables."
-    "|"
-    "|Optionally, the config table can also supply values for some or all"
-    "|of the builtin state variables.  For example, you could supply xyz"
-    "|in the config table.  If you do, the tangible will move to a new xyz"
-    "|coordinate.  If not, the tangible will retain its old xyz coordinate."
+    "|persistent state variables that are retained by the tangible's"
+    "|animation queue.  You must provide a table containing all the"
+    "|persistent values you want, and their initial values."
     "|") {
     LuaArg tanobj, config;
     LuaDefStack LS(L, tanobj, config);
@@ -144,46 +144,65 @@ LuaDefine(tangible_animinit, "tan,config",
     return LS.result();
 }
 
-    
-LuaDefine(tangible_animate, "tan,config",
+LuaDefine(tangible_animate, "tan,options,config",
     "|Add an animation step to the tangible."
     "|"
     "|The animation queue stores animation steps.  This function, "
     "|tangible.animate, adds one new animation step to the queue."
     "|"
-    "|It might be useful to read about 'animation state variables' before"
-    "|reading this explanation.  See doc(tangible.animstate)."
+    "|It might be useful to read doc(tangible.animinit) before reading"
+    "|more."
     "|"
     "|An animation step is just a list of key-value pairs.  Therefore,"
     "|the config table must be key-value pairs.  Keys must be simple"
     "|identifiers.  Values can be numbers, strings, booleans, or"
     "|coordinates."
     "|"
-    "|Some of the key-value pairs may match the name of an animation state"
+    "|Some of the key-value pairs may match the name of a persistent"
     "|variable.  If so, that key-value pair permanently changes the"
-    "|value of that animation state variable.  The new value will"
+    "|value of that persistent variable.  The new value will"
     "|be retained for all future animation steps."
     "|"
-    "|Some of the key-value pairs may NOT match the name of any animation"
-    "|state variable.  If so, that key-value pair is part of the"
+    "|Some of the key-value pairs may not match the name of any persistent"
+    "|variable.  If so, that key-value pair is part of the"
     "|animation step, but nothing is propagated forward to future animation"
     "|steps."
     "|"
+    "|The options can be nil, or options can be a table containing"
+    "|the following flags:"
+    "|"
+    "|    replace: if true, then the last step in the queue is removed,"
+    "|    and the new animation replaces it.  Persistent state is carried"
+    "|    over from the step that was replaced."
+    "|"
     "|") {
-    LuaArg tanobj, config;
-    LuaDefStack LS(L, tanobj, config);
+    LuaArg tanobj, options, steptab;
+    LuaVar option;
+    LuaDefStack LS(L, option, tanobj, options, steptab);
+    bool replace = false;
+    if (!LS.isnil(options)) {
+        LuaKeywordParser kp(LS, options);
+        if (kp.parse(option, "replace")) {
+            replace = LS.ckboolean(option);
+        }
+    }
     World *w = World::fetch_global_pointer(L);
     Tangible *tan = w->tangible_get(LS, tanobj, false);
     AnimState state = tan->anim_queue_.get_final_persistent();
-    eng::string error = state.apply_lua(LS, config, false);
+    eng::string error = state.apply_lua(LS, steptab, false);
     if (!error.empty()) {
         luaL_error(L, "%s", error.c_str());
     }
-    tan->anim_queue_.add(state);
+    if (replace) {
+        tan->anim_queue_.replace(state);
+    } else {
+        tan->anim_queue_.add(state);
+    }
     tan->update_plane_item();
     return LS.result();
 }
 
+
 LuaDefine(tangible_setclass, "tan,class",
     "|Set the class of the tangible."
     "|The class can be a 'class table' (ie, a table of methods), "