diff --git a/src/fixed.c b/src/fixed.c
index de30413..93fccdf 100644
--- a/src/fixed.c
+++ b/src/fixed.c
@@ -12,18 +12,15 @@
 
 twin_fixed_t twin_fixed_sqrt(twin_fixed_t a)
 {
-    twin_fixed_t max, min, mid;
-    twin_fixed_t sqr;
+    twin_fixed_t max = a, min = 0;
 
-    max = a;
-    min = 0;
     while (max > min) {
-        mid = (max + min) >> 1;
+        twin_fixed_t mid = (max + min) >> 1;
         if (mid >= 181 * TWIN_FIXED_ONE) {
             max = mid - 1;
             continue;
         }
-        sqr = twin_fixed_mul(mid, mid);
+        twin_fixed_t sqr = twin_fixed_mul(mid, mid);
         if (sqr == a)
             return mid;
         if (sqr < a)
@@ -36,13 +33,12 @@ twin_fixed_t twin_fixed_sqrt(twin_fixed_t a)
 
 twin_sfixed_t _twin_sfixed_sqrt(twin_sfixed_t as)
 {
-    twin_dfixed_t max = as, min = 0, mid;
+    twin_dfixed_t max = as, min = 0;
     twin_dfixed_t a = twin_sfixed_to_dfixed(as);
-    twin_dfixed_t sqr;
 
     while (max > min) {
-        mid = (max + min) >> 1;
-        sqr = mid * mid;
+        twin_dfixed_t mid = (max + min) >> 1;
+        twin_dfixed_t sqr = mid * mid;
         if (sqr == a)
             return (twin_sfixed_t) mid;
         if (sqr < a)
diff --git a/src/font.c b/src/font.c
index 642bbfe..e429cc5 100644
--- a/src/font.c
+++ b/src/font.c
@@ -330,7 +330,6 @@ void twin_path_ucs4(twin_path_t *path, twin_ucs4_t ucs4)
     twin_path_t *pen = NULL;
     twin_fixed_t width;
     twin_text_info_t info;
-    signed char op;
 
     _twin_text_compute_info(path, font, &info);
     if (info.snap)
@@ -346,6 +345,7 @@ void twin_path_ucs4(twin_path_t *path, twin_ucs4_t ucs4)
 
     x1 = y1 = 0;
     for (;;) {
+        signed char op;
         switch ((op = *g++)) {
         case 'm':
             x1 = FX(*g++, &info);
diff --git a/src/hull.c b/src/hull.c
index 160c946..04e8409 100644
--- a/src/hull.c
+++ b/src/hull.c
@@ -4,6 +4,7 @@
  * All rights reserved.
  */
 
+#include <stdbool.h>
 #include <stdlib.h>
 
 #include "twin_private.h"
@@ -16,7 +17,7 @@ typedef struct twin_slope {
 typedef struct _twin_hull {
     twin_spoint_t point;
     twin_slope_t slope;
-    int discard;
+    bool discard;
 } twin_hull_t;
 
 static void _twin_slope_init(twin_slope_t *slope,
@@ -29,23 +30,21 @@ static void _twin_slope_init(twin_slope_t *slope,
 
 static twin_hull_t *_twin_hull_create(twin_path_t *path, int *nhull)
 {
-    int i, j;
     int n = path->npoints;
     twin_spoint_t *p = path->points;
     twin_hull_t *hull;
-    int e;
 
-    e = 0;
-    for (i = 1; i < n; i++)
+    int e = 0;
+    for (int i = 1; i < n; i++)
         if (p[i].y < p[e].y || (p[i].y == p[e].y && p[i].x < p[e].x))
             e = i;
 
     hull = malloc(n * sizeof(twin_hull_t));
-    if (hull == NULL)
+    if (!hull)
         return NULL;
     *nhull = n;
 
-    for (i = 0; i < n; i++) {
+    for (int i = 0, j; i < n; i++) {
         /* place extremum first in array */
         if (i == 0)
             j = e;
@@ -59,9 +58,9 @@ static twin_hull_t *_twin_hull_create(twin_path_t *path, int *nhull)
 
         /* Discard all points coincident with the extremal point */
         if (i != 0 && hull[i].slope.dx == 0 && hull[i].slope.dy == 0)
-            hull[i].discard = 1;
+            hull[i].discard = true;
         else
-            hull[i].discard = 0;
+            hull[i].discard = false;
     }
 
     return hull;
@@ -102,9 +101,8 @@ static int _twin_hull_vertex_compare(const void *av, const void *bv)
 {
     twin_hull_t *a = (twin_hull_t *) av;
     twin_hull_t *b = (twin_hull_t *) bv;
-    int ret;
 
-    ret = _twin_slope_compare(&a->slope, &b->slope);
+    int ret = _twin_slope_compare(&a->slope, &b->slope);
 
     /* In the case of two vertices with identical slope from the
        extremal point discard the nearer point. */
@@ -116,10 +114,10 @@ static int _twin_hull_vertex_compare(const void *av, const void *bv)
         b_dist = ((twin_dfixed_t) b->slope.dx * b->slope.dx +
                   (twin_dfixed_t) b->slope.dy * b->slope.dy);
         if (a_dist < b_dist) {
-            a->discard = 1;
+            a->discard = true;
             ret = -1;
         } else {
-            b->discard = 1;
+            b->discard = true;
             ret = 1;
         }
     }
@@ -154,12 +152,11 @@ static int _twin_hull_next_valid(twin_hull_t *hull, int num_hull, int index)
 
 static void _twin_hull_eliminate_concave(twin_hull_t *hull, int num_hull)
 {
-    int i, j, k;
     twin_slope_t slope_ij, slope_jk;
 
-    i = 0;
-    j = _twin_hull_next_valid(hull, num_hull, i);
-    k = _twin_hull_next_valid(hull, num_hull, j);
+    int i = 0;
+    int j = _twin_hull_next_valid(hull, num_hull, i);
+    int k = _twin_hull_next_valid(hull, num_hull, j);
 
     do {
         _twin_slope_init(&slope_ij, &hull[i].point, &hull[j].point);
@@ -169,7 +166,7 @@ static void _twin_hull_eliminate_concave(twin_hull_t *hull, int num_hull)
         if (_twin_slope_compare(&slope_ij, &slope_jk) >= 0) {
             if (i == k)
                 break;
-            hull[j].discard = 1;
+            hull[j].discard = true;
             j = i;
             i = _twin_hull_prev_valid(hull, num_hull, j);
         } else {
diff --git a/src/path.c b/src/path.c
index 46d6f60..f840598 100644
--- a/src/path.c
+++ b/src/path.c
@@ -193,42 +193,34 @@ void twin_path_arc(twin_path_t *path,
                    twin_angle_t extent)
 {
     twin_matrix_t save = twin_path_current_matrix(path);
-    twin_fixed_t max_radius;
-    int32_t sides;
-    int32_t n;
-    twin_angle_t a;
-    twin_angle_t first, last, step, inc;
-    twin_angle_t epsilon;
 
     twin_path_translate(path, x, y);
     twin_path_scale(path, x_radius, y_radius);
 
-    max_radius = _twin_matrix_max_radius(&path->state.matrix);
-    sides = max_radius / twin_sfixed_to_fixed(TWIN_SFIXED_TOLERANCE);
+    twin_fixed_t max_radius = _twin_matrix_max_radius(&path->state.matrix);
+    int32_t sides = max_radius / twin_sfixed_to_fixed(TWIN_SFIXED_TOLERANCE);
     if (sides > 1024)
         sides = 1024;
 
-    n = 2;
+    int32_t n = 2;
     while ((1 << n) < sides)
         n++;
 
-    sides = (1 << n);
-
-    step = TWIN_ANGLE_360 >> n;
-    inc = step;
-    epsilon = 1;
+    twin_angle_t step = TWIN_ANGLE_360 >> n;
+    twin_angle_t inc = step;
+    twin_angle_t epsilon = 1;
     if (extent < 0) {
         inc = -inc;
         epsilon = -1;
     }
 
-    first = (start + inc - epsilon) & ~(step - 1);
-    last = (start + extent - inc + epsilon) & ~(step - 1);
+    twin_angle_t first = (start + inc - epsilon) & ~(step - 1);
+    twin_angle_t last = (start + extent - inc + epsilon) & ~(step - 1);
 
     if (first != start)
         twin_path_draw(path, twin_cos(start), twin_sin(start));
 
-    for (a = first; a != last; a += inc)
+    for (twin_angle_t a = first; a != last; a += inc)
         twin_path_draw(path, twin_cos(a), twin_sin(a));
 
     if (last != start + extent)
diff --git a/src/poly.c b/src/poly.c
index 7de5ce8..046878e 100644
--- a/src/poly.c
+++ b/src/poly.c
@@ -64,14 +64,11 @@ static int _twin_edge_build(twin_spoint_t *vertices,
                             twin_sfixed_t dy,
                             twin_sfixed_t top_y)
 {
-    int v, nv;
     int tv, bv;
-    int e;
-    twin_sfixed_t y;
 
-    e = 0;
-    for (v = 0; v < nvertices; v++) {
-        nv = v + 1;
+    int e = 0;
+    for (int v = 0; v < nvertices; v++) {
+        int nv = v + 1;
         if (nv == nvertices)
             nv = 0;
 
@@ -91,7 +88,7 @@ static int _twin_edge_build(twin_spoint_t *vertices,
         }
 
         /* snap top to first grid point in pixmap */
-        y = _twin_sfixed_grid_ceil(vertices[tv].y + dy);
+        twin_sfixed_t y = _twin_sfixed_grid_ceil(vertices[tv].y + dy);
         if (y < TWIN_POLY_START + top_y)
             y = TWIN_POLY_START + top_y;
 
@@ -233,14 +230,11 @@ static void _twin_edge_fill(twin_pixmap_t *pixmap,
                             int nedges)
 {
     twin_edge_t *active, *a, *n, **prev;
-    int e;
-    twin_sfixed_t y;
     twin_sfixed_t x0 = 0;
-    int w;
 
     qsort(edges, nedges, sizeof(twin_edge_t), _edge_compare_y);
-    e = 0;
-    y = edges[0].top;
+    int e = 0;
+    twin_sfixed_t y = edges[0].top;
     active = 0;
     for (;;) {
         /* add in new edges */
@@ -253,14 +247,13 @@ static void _twin_edge_fill(twin_pixmap_t *pixmap,
         }
 
         /* walk this y value marking coverage */
-        w = 0;
+        int w = 0;
         for (a = active; a; a = a->next) {
             if (w == 0)
                 x0 = a->x;
             w += a->winding;
-            if (w == 0) {
+            if (w == 0)
                 _span_fill(pixmap, y, x0, a->x);
-            }
         }
 
         /* step down, clipping to pixmap */
@@ -303,19 +296,14 @@ void twin_fill_path(twin_pixmap_t *pixmap,
                     twin_coord_t dx,
                     twin_coord_t dy)
 {
-    twin_edge_t *edges;
-    int nedges, n;
-    int nalloc;
-    int s;
-    int p;
     twin_sfixed_t sdx = twin_int_to_sfixed(dx + pixmap->origin_x);
     twin_sfixed_t sdy = twin_int_to_sfixed(dy + pixmap->origin_y);
 
-    nalloc = path->npoints + path->nsublen + 1;
-    edges = malloc(sizeof(twin_edge_t) * nalloc);
-    p = 0;
-    nedges = 0;
-    for (s = 0; s <= path->nsublen; s++) {
+    int nalloc = path->npoints + path->nsublen + 1;
+    twin_edge_t *edges = malloc(sizeof(twin_edge_t) * nalloc);
+    int p = 0;
+    int nedges = 0;
+    for (int s = 0; s <= path->nsublen; s++) {
         int sublen;
         int npoints;
 
@@ -325,7 +313,8 @@ void twin_fill_path(twin_pixmap_t *pixmap,
             sublen = path->sublen[s];
         npoints = sublen - p;
         if (npoints > 1) {
-            n = _twin_edge_build(path->points + p, npoints, edges + nedges, sdx,
+            int n =
+                _twin_edge_build(path->points + p, npoints, edges + nedges, sdx,
                                  sdy, twin_int_to_sfixed(pixmap->clip.top));
             p = sublen;
             nedges += n;
diff --git a/src/timeout.c b/src/timeout.c
index 33eb379..0629f9e 100644
--- a/src/timeout.c
+++ b/src/timeout.c
@@ -34,10 +34,9 @@ void _twin_run_timeout(void)
 {
     twin_time_t now = twin_now();
     twin_timeout_t *timeout;
-    twin_timeout_t *first;
     twin_time_t delay;
 
-    first = (twin_timeout_t *) _twin_queue_set_order(&head);
+    twin_timeout_t *first = (twin_timeout_t *) _twin_queue_set_order(&head);
     for (timeout = first; timeout && twin_time_compare(now, >=, timeout->time);
          timeout = (twin_timeout_t *) timeout->queue.order) {
         delay = (*timeout->proc)(now, timeout->closure);