Level 1. OUT, CUT, COT, SCOT, COST, SCOUT, OUST
Level 2. ROD, OUR, POUR, PROD, DOUR, DROP, PROUD, PRO
Level 3. TIP, RIP, PIT, PUT, PURITY, TRY
Level 4. HELM, BLUE, HUMBLE, MULE
Level 5. RAIN, RUIN, FAIN, FAIR, UNFAIR
Level 6. CHAR, BARN, ARCH, BACH, BRANCH, CRAB
Level 7. WHIT, WITH, TWIG, WHET, WEIGTH, WHIG
Level 8. HEAR, RATE, HATE, HEART, EARTH, FATHER, AFTER
