diff --git a/src/corelib/input.c b/src/corelib/input.c
index d4b5bf7..df5c666 100644
--- a/src/corelib/input.c
+++ b/src/corelib/input.c
@@ -23,7 +23,8 @@ void add_key_listener(SDL_Scancode negative, SDL_Scancode positive,
 	g_key_listeners_endptr->axis.delegate = delegate;
 	g_key_listeners_endptr->axis.positive = positive;
 	g_key_listeners_endptr->axis.negative = negative;
-	g_key_listeners_endptr->axis.last = 0;
+	g_key_listeners_endptr->axis.last_positive =
+		g_key_listeners_endptr->axis.last_negative = 0;
 	++g_key_listeners_endptr;
 }
 
@@ -70,21 +71,6 @@ void input_init() {
 	g_key_states = SDL_GetKeyboardState(NULL);
 }
 
-static inline
-void _process_axis_listener(input_listener_t* listener) {
-	int val = 0;
-	if(g_key_states[listener->axis.negative]) {
-		val = -1;
-	}
-	if(g_key_states[listener->axis.positive]) {
-		val += 1;
-	}
-	if(val != listener->axis.last) {
-		listener->axis.last = val;
-		listener->axis.delegate(val);
-	}
-}
-
 static inline
 void _process_mouse_listener(input_listener_t* listener, float dx, float dy) {
 	if(dx != 0.0 && dy != 0.0) {
@@ -92,23 +78,6 @@ void _process_mouse_listener(input_listener_t* listener, float dx, float dy) {
 	}
 }
 
-static inline
-void _process_button_listener(input_listener_t* listener) {
-	uint32_t state = SDL_GetMouseState(NULL, NULL);
-	int is_down = (state & (listener->button.button)) != 0;
-	if(is_down != listener->button.last) {
-		listener->button.delegate(is_down);
-	}
-	listener->button.last = is_down;
-}
-
-static inline
-void _process_scroll_listener(input_listener_t* listener) {
-	if(_scroll_delta != 0) {
-		listener->scroll.delegate(_scroll_delta);
-	}
-}
-
 void update_input() {
 	float dx, dy;
 	int px, py;
@@ -118,19 +87,8 @@ void update_input() {
 	dx = (float)(px - _last_mouse_x)/width; dy = (float)(py - _last_mouse_y)/width;
 
 	for(input_listener_t* listener = g_key_listeners; listener != g_key_listeners_endptr; ++listener) {
-		switch(listener->type) {
-			case INPUT_LISTENER_AXIS:
-				_process_axis_listener(listener);
-				break;
-			case INPUT_LISTENER_MOUSE:
+		if(listener->type == INPUT_LISTENER_MOUSE) {
 				_process_mouse_listener(listener, dx, dy);
-				break;
-			case INPUT_LISTENER_SCROLL:
-				_process_scroll_listener(listener);
-				break;
-			case INPUT_LISTENER_BUTTON:
-				_process_button_listener(listener);
-				break;
 		}
 	}	
 
@@ -140,13 +98,58 @@ void update_input() {
 	_scroll_delta = 0;
 }
 
+static inline
+void _handle_key_event(const SDL_Event event) {
+	for(input_listener_t* listener = g_key_listeners; listener < g_key_listeners_endptr; ++listener) {
+		if(listener->type == INPUT_LISTENER_AXIS) {
+			const SDL_Scancode scode = event.key.keysym.scancode;
+			if(listener->axis.positive == scode) {
+				listener->axis.last_positive = event.key.state == SDL_PRESSED;
+			}
+			if(listener->axis.negative == scode) {
+				listener->axis.last_negative = event.key.state == SDL_PRESSED;
+			}
+			listener->axis.delegate(listener->axis.last_positive - listener->axis.last_negative);
+		}
+	}
+}
+
+static inline
+void _handle_scroll_event(const SDL_Event event) {
+	_scroll_delta = event.wheel.y;
+	for(input_listener_t* listener = g_key_listeners; listener < g_key_listeners_endptr; ++listener) {
+		if(listener->type == INPUT_LISTENER_SCROLL) {
+			listener->scroll.delegate(_scroll_delta);
+		}
+	}
+}
+
+static inline
+void _handle_mousebutton_event(const SDL_Event event) {
+	for(input_listener_t* listener = g_key_listeners; listener < g_key_listeners_endptr; ++listener) {
+		if(listener->type == INPUT_LISTENER_BUTTON
+		|| listener->button.button == event.button.button) {
+			listener->button.last = event.button.state == SDL_PRESSED;
+			listener->button.delegate(listener->button.last);
+		}
+	}
+}
+
 void input_notify_event(SDL_Event event) {
 	switch(event.type) {
 		default:
 			return;
+		case SDL_KEYUP:
+		case SDL_KEYDOWN:
+			_handle_key_event(event);
+			return;
 		case SDL_MOUSEWHEEL:
-			_scroll_delta = event.wheel.y;
-			break;
+			_handle_scroll_event(event);
+			return;
+		case SDL_MOUSEBUTTONUP:
+		case SDL_MOUSEBUTTONDOWN:
+			_handle_mousebutton_event(event);
+			return;
 	}
 }
 
diff --git a/src/corelib/input.h b/src/corelib/input.h
index 85d3cc8..9be54d6 100644
--- a/src/corelib/input.h
+++ b/src/corelib/input.h
@@ -25,7 +25,7 @@ typedef struct input_listener_t {
 		struct {
 			input_axis_delegate_t delegate;
 			SDL_Scancode positive, negative;
-			int last;
+			int last_positive, last_negative;
 		} axis;
 		struct {
 			input_mouse_delegate_t delegate;
diff --git a/src/corelib/math/vec.h b/src/corelib/math/vec.h
new file mode 100644
index 0000000..082c589
--- /dev/null
+++ b/src/corelib/math/vec.h
@@ -0,0 +1,54 @@
+#ifndef _vec_math_h
+#define _vec_math_h
+
+#include "math.h"
+
+static inline
+void clamp_magnitude(float* xx, float* yy, float max_magnitude) {
+	float x = *xx, y = *yy;
+	const float m = sqrtf(x*x + y*y);
+	if(m > max_magnitude) {
+		x /= m; y /= m;
+		x *= max_magnitude; y *= max_magnitude;
+	} else {
+		*xx = x; *yy = y;
+	}
+}
+
+static inline
+void normalize(float x, float y, float* xx, float* yy) {
+	if(x != 0 || y != 0) {
+		const float m = sqrtf(x*x + y*y);
+		*xx = x / m; *yy = y / m;
+	} else {
+		*xx = x; *yy = y;
+	}
+}
+
+#define NORMALIZE(_xx, _yy) \
+if(_xx != 0 || _yy != 0) { \
+	const float m = sqrtf(_xx*_xx + _yy*_yy); \
+	_xx /= m; _yy /= m; \
+} else { \
+	_xx = 0; _yy = 0; \
+}
+
+static inline
+int move_towards(float* out_x, float* out_y, float x, float y, float tx, float ty, float max_delta) {
+	const float diff_x = tx - x,
+		diff_y = ty - y;
+	const float m = sqrtf(diff_x*diff_x + diff_y*diff_y);
+	const float dir_x = diff_x / m * max_delta,
+		dir_y = diff_y / m * max_delta;
+	if(fabsf(dir_x) < fabsf(diff_x) || fabsf(dir_y) < fabsf(diff_y)) {
+		*out_x = x + dir_x;
+		*out_y = y + dir_y;
+		return 0;
+	} else {
+		*out_x = tx;
+		*out_y = ty;
+		return 1;
+	}
+}
+
+#endif /* _vec_math_h */
diff --git a/src/corelib/world.c b/src/corelib/world.c
index 85fbed4..a46e6bc 100644
--- a/src/corelib/world.c
+++ b/src/corelib/world.c
@@ -1,4 +1,5 @@
 #include "world.h"
+#include "math/vec.h"
 
 object_t g_objects[WORLD_NUM_OBJECTS];
 
@@ -106,6 +107,93 @@ float fclampf(float x, float min_, float max_) {
 	return fminf(max_, fmaxf(min_, x));
 }
 
+static inline
+float _circle_aabb_overlap(const object_t* circle, const object_t* aabb, float* out_px, float* out_py) {
+	// generate a point on the edge of the rectangle that is closest to the circle
+	const float bbminx = aabb->collider.aabb.x + aabb->sprite.x, bbmaxx = bbminx + aabb->collider.aabb.w,
+	            bbminy = aabb->collider.aabb.y + aabb->sprite.y, bbmaxy = bbminy + aabb->collider.aabb.h;
+	// the centre of the circle in world space
+	const float cx = circle->sprite.x + circle->collider.circle.x,
+	            cy = circle->sprite.y + circle->collider.circle.y;
+	// the point on the rectangle closest to the centre of the circle
+	const float x = fclampf(cx, bbminx, bbmaxx),
+	            y = fclampf(cy, bbminy, bbmaxy);
+	// the relative position of the point on the rectangle 
+	const float dif_x = cx - x,
+	            dif_y = cy - y;
+	// absolute difference for use in calculating euclidean distance 
+	const float dist_x = fabsf(dif_x),
+	            dist_y = fabsf(dif_y);
+	// euclidean distance
+	const float dist = sqrt(dist_x*dist_x + dist_y*dist_y);
+	const float solve_distance = circle->collider.circle.radius - dist;
+	// distance to solve collision
+	float solve_x, solve_y;
+	normalize(dif_x, dif_y, &solve_x, &solve_y);
+	*out_px = solve_x * solve_distance;
+	*out_py = solve_y * solve_distance;
+	return solve_distance;
+}
+
+static inline
+float _circle_circle_overlap(const object_t* a, const object_t* b, float* out_px, float* out_py) {
+	const float x1 = a->collider.circle.x + a->sprite.x, y1 = a->collider.circle.y + a->sprite.y;
+	const float x2 = b->collider.circle.x + b->sprite.x, y2 = b->collider.circle.y + b->sprite.y;
+	const float dif_x = x1 - x2, dif_y = y1 - y2;
+	const float difference = sqrtf(fabsf(dif_x*dif_x) + fabsf(dif_y*dif_y));
+	const float target_difference = a->collider.circle.radius + b->collider.circle.radius;
+	float dir_x, dir_y;
+	normalize(dif_x, dif_y, &dir_x, &dir_y);
+	*out_px = dir_x * target_difference;
+	*out_py = dir_y * target_difference;
+	return target_difference;
+}
+
+static inline
+float _aabb_aabb_overlap(const object_t* a, const object_t* b, float* out_px, float* out_py) {
+	float right = (a->collider.aabb.x + a->collider.aabb.w + a->sprite.x) - (b->collider.aabb.x + b->sprite.x);
+	float left = (a->collider.aabb.x + a->sprite.x) - (b->collider.aabb.x + b->collider.aabb.w + b->sprite.x);
+	float top = (a->collider.aabb.y + a->sprite.y) - (b->collider.aabb.y + b->collider.aabb.w + b->sprite.y);
+	float bottom = (a->collider.aabb.y + a->collider.aabb.h) - (b->collider.aabb.y + b->sprite.y);
+
+	float ret = right;
+	*out_px = right;
+	*out_py = 0.f;
+	if(fabsf(left) < fabsf(ret)) {
+		*out_px = left;
+		*out_py = 0.f;
+		ret = left;
+	}
+	if(fabsf(top) < fabsf(ret)) {
+		*out_px = 0.f;
+		*out_py = top;
+		ret = top;
+	}
+
+	if(fabsf(bottom) < fabsf(ret)) {
+		*out_px = 0.f;
+		*out_py = bottom;
+		return bottom;
+	}
+
+	return ret;
+}
+
+static inline
+float _get_overlap(const object_t* a, const object_t* b, float* out_px, float* out_py) {
+	if(a->collider.type == COLLIDERTYPE_AABB && b->collider.type == COLLIDERTYPE_AABB) {
+		return _aabb_aabb_overlap(a, b, out_px, out_py);
+	} else if(a->collider.type == COLLIDERTYPE_AABB && b->collider.type == COLLIDERTYPE_CIRCLE) {
+		float penetration_distance = _circle_aabb_overlap(b, a, out_px, out_py);
+		*out_px = -(*out_px);
+		*out_py = -(*out_py);
+	} else if(a->collider.type == COLLIDERTYPE_CIRCLE && b->collider.type == COLLIDERTYPE_AABB) {
+		return _circle_aabb_overlap(a, b, out_px, out_py);
+	} else if(a->collider.type == COLLIDERTYPE_CIRCLE && b->collider.type == COLLIDERTYPE_CIRCLE) {
+		return _circle_circle_overlap(a, b, out_px, out_py);
+	}
+}
+
 static inline
 short _collision_circle_aabb(const object_t* circle, const object_t* aabb) {
 	// generate a point on the edge of the rectangle that is closest to the circle
@@ -166,36 +254,74 @@ void update_collision() {
 	}
 }
 
-object_t* interpolate_move(object_t* object, float target_x, float target_y, float max_step_size) {
+static inline
+void _slide_collision(object_t* this, object_t* other, float old_x, float old_y, float new_x, float new_y) {
+	float dx, dy;
+	const float d = _get_overlap(this, other, &dx, &dy);
+	this->sprite.x += dx;
+	this->sprite.y += dy;
+	
+	return;
+	this->sprite.x = old_x;
+	this->sprite.y = new_y;
+	if(!_collision_check(other, this)) {
+		return;
+	}
+
+	this->sprite.x = new_x;
+	this->sprite.y = old_y;
+	if(!_collision_check(other, this)) {
+		return;
+	}
+
+	this->sprite.x = old_x;
+	this->sprite.y = old_y;
+	if(!_collision_check(other, this)) {
+		return;
+	}
+}
+
+void interpolate_move(object_t* object, const float target_x, const float target_y, const float max_step_size, const int slide) {
 	// calculate step delta
 	float dx = target_x - object->sprite.x, dy = target_y - object->sprite.y;
+	if(dx == 0 && dy == 0)
+		return;
 	// calculate direction x,y
 	float m = sqrtf(dx*dx + dy*dy);
-	dx /= m; dy /= m;
+	if(dx != 0)
+		dx /= m;
+	if(dy != 0)
+		dy /= m;
 	dx *= max_step_size; dy *= max_step_size;
+	int step_count = max_step_size / m;
 
 	// ensure this object would ever collide
 	// if it wouldn't collide anyway, just set position
 	if(!_can_collide(object)) {
 		object->sprite.x = target_x;
 		object->sprite.y = target_y;
-		return NULL;
+		return;
 	}
 
 	/*
 	 * 1. move towards target
 	 * 2. check collision with every other object
 	 */
-	while(object->sprite.x != target_x || object->sprite.y != target_y) {
+	for(int steps = 0; steps < step_count && (object->sprite.x != target_x || object->sprite.y != target_y); ++steps) {
 		// move towards target, snap to target if distance is too low
 		const float old_x = object->sprite.x, old_y = object->sprite.y;
+		float new_x, new_y;
+
 		const float distx = fabsf(object->sprite.x - target_x), disty = fabsf(object->sprite.y - target_y);
-		if(distx < fabsf(dx) && disty < fabsf(dy)) {
+		const float sqdist = distx*distx + disty*disty;
+		if(sqdist > max_step_size) {
 			object->sprite.x += dx;
 			object->sprite.y += dy;
+			new_x = object->sprite.x;
+			new_y = object->sprite.y;
 		} else {
-			object->sprite.x = target_x;
-			object->sprite.y = target_y;
+			new_x = object->sprite.x = target_x;
+			new_y = object->sprite.y = target_y;
 		}
 
 		// loop over all objects and check collision if applicable
@@ -206,13 +332,14 @@ object_t* interpolate_move(object_t* object, float target_x, float target_y, flo
 			if(_can_collide(other) && object != other && _collision_check(other, object)) {
 				object_broadcast_collision(other, object);
 				object_broadcast_collision(object, other);
-				object->sprite.x = old_x;
-				object->sprite.y = old_y;
-				return other;
+				if(slide) {
+					_slide_collision(object, other, old_x, old_y, new_x, new_y);
+				} else {
+					object->sprite.x = old_x;
+					object->sprite.y = old_y;
+					return;
+				}
 			}
 		}
 	}
-
-	// no collision, return nothing
-	return NULL;
 }
diff --git a/src/corelib/world.h b/src/corelib/world.h
index 2c57f31..27de091 100644
--- a/src/corelib/world.h
+++ b/src/corelib/world.h
@@ -62,6 +62,6 @@ void draw_objects();
 
 void update_collision();
 
-object_t* interpolate_move(object_t* object, float target_x, float target_y, float max_step_size);
+void interpolate_move(object_t* object, float target_x, float target_y, float max_step_size, int slide);
 
 #endif /* _world_h */
diff --git a/src/engine.c b/src/engine.c
index 8d61289..8a5d514 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -5,11 +5,27 @@
 #include "corelib/input.h"
 #include "time.h"
 
-static float _delta_time = 0;
+static double _delta_time = 0;
+static double _min_frame_interval = 0;
 static struct timespec start_last_frame;
 
+#define CURRENT_TIME(__out) { struct timespect ts; timespec_get(&ts, TIME_UTC); __out = ts.tv_sec + tv.nsec * 1E-09; }
+
+inline static
+double timespec_to_sec(struct timespec spec) {
+	return (double)spec.tv_sec + (double)spec.tv_nsec * 1E-09;
+}
+
 inline float delta_time() {
-	return _delta_time;
+	return (float)_delta_time;
+}
+
+void set_frame_interval(double frame_interval) {
+	_min_frame_interval = frame_interval;
+}
+
+void set_frame_rate_limit(int fps) {
+	_min_frame_interval = 1.0/(double)fps;
 }
 
 static inline
@@ -58,8 +74,7 @@ int _engine_run() {
 	struct timespec next_time;
 	while(g_context.running) {
 		timespec_get(&next_time, TIME_UTC);
-		_delta_time = (next_time.tv_nsec - start_last_frame.tv_nsec) * 1E-9;
-		if(next_time.tv_nsec < start_last_frame.tv_nsec) _delta_time = 0;
+		_delta_time = timespec_to_sec(next_time) - timespec_to_sec(start_last_frame);
 		start_last_frame = next_time;
 		_handle_events();
 		update_input();
@@ -70,6 +85,11 @@ int _engine_run() {
 		update_objects();	// update world objects
 		draw_objects();		// draw world objects
 		swap_buffer();
+		do {
+			timespec_get(&next_time, TIME_UTC);
+			_delta_time = timespec_to_sec(next_time) - timespec_to_sec(start_last_frame);
+			SDL_PumpEvents();
+		} while(_delta_time < _min_frame_interval);
 	}
 	return 0;
 }
diff --git a/src/engine.h b/src/engine.h
index 87bf672..8667836 100644
--- a/src/engine.h
+++ b/src/engine.h
@@ -6,6 +6,8 @@ extern "C" {
 #endif
 
 extern float delta_time();
+extern void set_frame_interval(double frame_interval);
+extern void set_frame_rate_limit(int fps);
 
 /* TO BE DEFINED IN GAME */