diff --git a/platformer.c b/platformer.c
index 2db6628..ee0381c 100644
--- a/platformer.c
+++ b/platformer.c
@@ -29,9 +29,9 @@ static char tilemap[] = "          "
                         "          "
                         "          "
                         "          "
-                        "gg        "
-                        "          "
-                        "          "
+                        "gg    g   "
+                        "   g     g"
+                        "        g "
                         "     g    "
                         "    g g   "
                         "gggggggggg";
@@ -49,6 +49,10 @@ static void on_disconnect(void *context) {
 
 static bool left_held, right_held, jump_held;
 
+static double jump_maxhold = 0.3;
+static double jump_maxheight = 21;
+static double jump_duration = 0.4;
+
 static void on_keyboard(void *context, uint32_t window, uint32_t codepoint) {
 	(void) context;
 	if (window != main_window)
@@ -62,7 +66,14 @@ static void on_keyboard(void *context, uint32_t window, uint32_t codepoint) {
 		case -KBKEY_RIGHT: right_held = false; break;
 		case KBKEY_SPACE: jump_held = true; break;
 		case -KBKEY_SPACE: jump_held = false; break;
+		case KBKEY_Q: jump_maxhold += 0.1; break;
+		case KBKEY_A: jump_maxhold -= 0.1; break;
+		case KBKEY_W: jump_maxheight += 0.1; break;
+		case KBKEY_S: jump_maxheight -= 0.1; break;
+		case KBKEY_E: jump_duration += 0.1; break;
+		case KBKEY_D: jump_duration -= 0.1; break;
 	}
+	printf("hold %i height %i duration %i\n", (int)(jump_maxhold * 10), (int)(jump_maxheight * 10), (int)(jump_duration * 10));
 }
 
 static void on_quit(void *context, uint32_t window) {
@@ -91,21 +102,67 @@ static char sample_tilemap(size_t x, size_t y) {
 	return tilemap[ty * TILES + tx];
 }
 
-static double player_x, player_y;
+static bool jumping = false;
+static bool on_ground = false;
+static double jump_start_y;
+static double in_jump;
+static double player_x = 0, player_y = 80;
 static double player_dx, player_dy;
 static void update(struct timespec now, struct timespec dt_timespec) {
 	(void) now;
 	double dt = timespec2double(dt_timespec);
-
 	player_x += player_dx * dt;
-	player_y += player_dy * dt;
+	//player_y += player_dy * dt;
 
 	if (left_held) player_dx = -30;
 	else if (right_held) player_dx = 30;
 	else player_dx = 0;
 
-	if (jump_held) player_dy = -30;
-	else player_dy = 30;
+	if (on_ground && jump_held && !jumping) {
+		jumping = true;
+		in_jump = 0;
+		jump_start_y = player_y;
+	}
+	if (!on_ground && !jumping) {
+		// TODO: implement proper falling
+		jumping = true;
+		in_jump = jump_duration;
+		jump_start_y = player_y + jump_maxheight;
+	}
+	if (jumping) {
+		in_jump += dt;
+		// Jump is a quadratic arc
+		// h = at^2 + bt + c
+		//
+		// Beginning of jump, zero height
+		// t = 0, h = 0
+		// 0 = a0^2 + b0 + c
+		// c = 0
+		//
+		// At 2*duration, zero height
+		// t = 2T, h = 0
+		// 0 = a(2T)^2 + b(2T) + 0
+		// 0 = 4aT^2 + 2bT
+		// 0 = 2aT^2 + bT
+		// 0 = 2aT + b
+		// b = -2aT
+		//
+		// At duration, maximum height
+		// t = T, h = H
+		// H = aT^2 + bT + 0
+		// H = aT^2 - 2aT^2
+		// H = -aT^2
+		// a = -H / (T^2)
+		// b
+		double a = -jump_maxheight / (jump_duration * jump_duration);
+		double b = -2 * a * jump_duration;
+		double jump_height = a * in_jump * in_jump + b * in_jump;
+		player_y = jump_start_y - jump_height;
+		// player_dy is negative of derivative of jump_height
+		// H = a*t^2 + b*t
+		// H' = 2*a*t + b
+		player_dy = -2 * a * in_jump - b;
+	}
 
 	// Collision against walls of the map
 	if (player_x < 0) {
@@ -129,7 +186,7 @@ static void update(struct timespec now, struct timespec dt_timespec) {
 	size_t left_cx = px - 1;
 	size_t right_cx = px + TILE_SIDE;
 	size_t leftright_top_cy = py;
-	size_t leftright_bottom_cy = py + TILE_SIDE - 1;
+	size_t leftright_bottom_cy = py + TILE_SIDE - 2;
 	if ((sample_tilemap(left_cx, leftright_top_cy) != ' ' ||
 	     sample_tilemap(left_cx, leftright_bottom_cy) != ' ') &&
 		player_dx < 0) {
@@ -152,14 +209,15 @@ static void update(struct timespec now, struct timespec dt_timespec) {
 	size_t top_cy = py - 1;
 	size_t bottom_cy = py + TILE_SIDE;
 
-	bool on_ground = false;
-	if ((sample_tilemap(topbottom_left_cx, bottom_cy) != ' ' ||
-	     sample_tilemap(topbottom_right_cx, bottom_cy) != ' ') &&
-		player_dy > 0) {
+	on_ground = false;
+	if (sample_tilemap(topbottom_left_cx, bottom_cy) != ' ' ||
+	    sample_tilemap(topbottom_right_cx, bottom_cy) != ' ') {
 		on_ground = true;
-		size_t snapped_py = py / TILE_SIDE * TILE_SIDE;
-		player_y = snapped_py;
-		player_dy = 0;
+		if (player_dy > 0) {
+			jumping = false;
+			size_t snapped_py = py / TILE_SIDE * TILE_SIDE;
+			player_y = snapped_py;
+		}
 	}
 	if ((sample_tilemap(topbottom_left_cx, top_cy) != ' ' ||
 	     sample_tilemap(topbottom_right_cx, top_cy) != ' ') &&