April r/ProcGen challenge

HTML

<canvas id="c" width="1000" height="400"/>

JavaScript

// "Tower" style inspiration: https://s-media-cache-ak0.pinimg.com/564x/4c/bb/3d/4cbb3d1b045121b57c3173da81016bc6.jpg

var scrollSpeed = 0.8;

var seed = 0;
var seedSalt = Math.floor(Math.random() * 10000);

var currentBlock = 0;
var currentX = 0;

var canvas = document.getElementById('c');
var c2 = canvas.getContext('2d');
var canvasHeight = 400;
var color_stone = '#999';
var color_grass = '#5a5';
var color_wood = '#974';
var color_pine = '#494';
var color_pine_dark = '#383';
var color_pine_light = '#5a5';
var color_water = '#8085AF';

// Tower
var color_tower = '#EEDBCD';
var color_tower_light = '#F8E8DB';
var color_tower_dark = '#BEA495';
var color_towerRoof = '#BD5441';
var color_towerRoof_light = '#E05E4E';
var color_towerRoof_dark = '#A13930';
var color_towerRoofDeco = '#812B2A';
var color_towerWindow = '#584646';
var color_towerWindow_border = '#8E817B';
var color_towerFlag = '#FCCF7C';
var color_towerDoor = '#907267';
var shadow_alpha = 0.2; 
var color_shadow = "rgba(40, 20, 40, " + shadow_alpha + ")"; 

// Farm
var color_wheat = '#F7EF99';
var color_wheat_base = '#DBCD53';
var color_fence = '#966537';
var color_farmhouse = '#AF9470';
var color_farmhouse_roof = '#726049';

// River
var color_bridge_base = '#999689';
var color_bridge = '#776';

// Sky
var color_sky_day_bottom = '#D6F0FF';
var color_sky_day_top = '#B5E3FF';
var color_sky_sunset_bottom = '#FFAA88';
var color_sky_sunset_top = '#FF91B0';

var color_sky_bottom = color_sky_day_bottom;
var color_sky_top = color_sky_day_top;

var colors = [color_stone, color_grass];

var blockWidth = 200;

setInterval(DrawFrame, 10);
function DrawFrame() {  
  // Store the current transformation matrix
	c2.save();

	// Use the identity matrix while clearing the canvas
	c2.setTransform(1, 0, 0, 1, 0, 0);
	c2.clearRect(0, 0, canvas.width, canvas.height);

	// Restore the transform
	c2.restore();
  
  c2.translate(-scrollSpeed, 0);
  
  // Draw sky background
  var gradient = c2.createLinearGradient(0, 0, 0,...