+
+update:
+ mov eax, [ship_y]
+
+ check_key SC_W
+ jnc .not_w
+ sub eax, PLAYER_MOVE_SPEED
+ jns .not_w
+ xor eax, eax
+.not_w: check_key SC_S
+ jnc .not_s
+ add eax, PLAYER_MOVE_SPEED
+ cmp eax, 200 << 8
+ jb .not_s
+ mov eax, 200 << 8
+.not_s:
+ mov [ship_y], eax
+ mov eax, [ship_x]
+
+ check_key SC_A
+ jnc .not_a
+ sub eax, PLAYER_MOVE_SPEED
+ jns .not_a
+ xor eax, eax
+.not_a: check_key SC_D
+ jnc .not_d
+ add eax, PLAYER_MOVE_SPEED
+ cmp eax, 320 << 8
+ jb .not_d
+ mov eax, 320 << 8
+.not_d:
+ mov [ship_x], eax
+ ret
+
+ section .data
+ align 4
+ship_x: dd 160 << 8
+ship_y: dd 100 << 8