All five achievements unlock as you play the game. First four are for stacking different coloured shells and the last one is for completing all 30 levels.

I wasn't quite sure how to format everything, but the / detonates stacking a shell on top of another. I don't differentiate whether the stacked shells are the same or different.

↑ → ↑ → ↓ /

→ → ↑ ↓ ← ← ↑ ↓ ← ← ↑ ↑ → → → /

← ← ↓ ↓ → → ↑ ← ← /
↓ → → ↓ ← /

↑ ↑ ← /
→ ↓ ↓ ← ↑ → ↑ ← /
↓ ↓ ← ← ↑ ↑ /

↑ ← /
↓ ← ← ↑ ↑ ↑ → ↓ /
↑ → ↓ ↓ → ↓ ← /

↑ ↑ ↑ ← ↓ /
↑ ← ← ← ↓ ↓ → → /
↓ → → ↑ ↑ ↓ ↓ ← ← ↑ ← ↑ ← ↑ → → → /

↑ ↑ ← ↓ → ↓ ← → ↑ ↑ ↑ ↑ ← ← ← ← ↓ ↓ → ↓ ← ↓ → /
← ↑ ↑ ↑ ↑ → → → ↓ ↓ ↓ → ↓ ← /
↑ ↑ ↑ ↑ ← ← ↓ ↓ ↓ /

→ → ↑ ↑ ↑ ← ← ↓ /
↑ → → ↓ ↓ ↓ ← ← ← ← ↑ ↑ → ↓ ↓ → → → ↑ ↑ ↑ ← ← ↓ /
→ ↑ → ↓ ↓ ↑ ← ← ← ↓ ↓ → → /

↑ ↑ ↑ ← ← ↓ → ↑ → ↓ ← ↓ → /
↓ ↓ ← ↑ ↑ → ↑ ↑ ← ← ↓ → ↑ → ↓ ↓ ← ↓ → ↑ ↑ ↑ → → ↓ ← ← ↑ ← ↓ ↓ → ↓ ← /
↓ → → ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ → /

← ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ ↓ → ↑ /
← ↑ ↑ → ↑ → → → ↓ ← /
→ ↓ ↓ ← ← ↓ ← ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ → → ↓ → ↑ /

→ → ↑ /
→ /
↓ ← ← ← ↑ ↑ ↑ → → → → ↓ /
↑ ← ↓ ↓ ← ↓ → /
← ← ← ↑ ↑ → /
← ↓ → → ↓ → ↑ /

↑ ↑ → /
↑ → → → ↓ ← /
↑ ← ← ↓ /
← ↓ ↓ → → ↑ /
↓ → ↑ ↑ → ↑ ← /

← ↑ /
↓ ← ← ↑ ↑ → /
← ↓ ↓ → → → → ↑ ↑ ← /
→ ↓ ↓ ← ← ← ← ↑ ↑ → /
← ↓ ↓ → → → → ↑ ↑ ↑ ← ↓ /
↑ ↑ ← ← ← ↓ ← ↓ → → /
← ↑ ↑ → → → → ↓ ↓ ← /
↑ ↑ ← ← ↓ /

→ ↑ ↑ ↑ ↑ ← ↓ /
← ← ← ↑ ← ↓ ↓ ↓ ↑ ↑ → → → → → ↓ ↓ ↓ ← ↑ /
→ ↑ ↑ ↑ ← ↓ /
→ ↓ ↓ ↓ ← ↑ /
→ ↑ ↑ ↑ ← ↓ /
→ ↓ ↓ ↓ ← ↑ /
→ ↑ ↑ ← ← ← ← ↑ ← ↓ ↓ ↓ /
→ → → ← ← ← ↑ ↑ → → → → → ↓ ↓ ↓ ← ↑ /
→ ↑ ↑ ↑ ← ↓ /
← ← ← ↓ ← ↓ → → → /

↑ ↑ → /
↓ ← ↓ → → → → ← ← ↑ /
← ↑ ↑ → → → ↓ /
← /
↑ ← ← ← ↓ ↓ ↓ → → → ↑ ↑ ↓ ← ← ← ↑ ↑ → → → → /
← ← ← ↓ ← ↓ → → → /
↑ → → ↓ /

← ↑ → ↓ → ↑ /
→ ↑ ↑ ↑ ← ↓ /
↑ ↑ ← ← ↓ ↓ /
↑ ↑ → → ↓ ↓ → ↓ ↓ ← ← ↓ ← ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ → → ↓ → ↑ /
← ← ← ↑ ↑ ↑ → → ↑ → ↓ /

→ → ↑ /
↓ ← ← ↑ /
→ ↓ → ↑ /
↓ ← ← ← ← ↑ → ↓ → ↑ /
← ← ↑ ↑ → → → /
↓ ↑ ← ← ↓ ← ↓ → → /

→ → ↑ ↑ ← ↑ ← ↓ ↑ ← ← ↓ ↓ → /
↑ ← ↑ → → → /
↓ → ↓ ← /
↑ ← ← ↓ ↑ → → ↓ ↓ ← ← /

← ← ↑ → /
↓ → → → ↑ ← /
↑ ↑ ↓ ↓ ↓ ← ← ← ↑ → /
↓ → → ↑ ↑ ↑ /
← /

← ← ← ← ↑ → /
↓ → → → ↑ ← /
↓ ← ← ← ↑ → /
↓ → → ↑ /
→ ↑ ↑ ↑ ← ↓ /
→ ↓ ↓ ← /
↓ ← ← ← ↑ → /
↓ → → → ↑ ← /
↓ ← ← ← ↑ → /
↓ → → → ↑ ← /
↓ ← ← ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ → /
↓ → → → ↑ ← /
↓ ← ← ↑ /
← ↑ ↑ → /

↑ /
↓ ← ← ↑ → ↓ → ↑ /
← ↑ ← ↑ → /

↑ ↑ ← /
↓ ↓ ← ← ↑ ↓ ← ↑ ↑ → /
↓ ↓ → → → ↑ ↑ ← /
↓ ↓ ← ← ← ↑ ↑ → /
↓ ↓ → → → ↑ ↑ ← /
↓ ↓ ← ← ↑ ↑ ↓ ↓ → → ↑ ↑ ↑ ← ← /

← ← ↑ → ↓ → ↑ /
→ ↑ → ↑ ↑ ← ← ↓ ← ↓ ↑ → ↑ → → ↓ ↓ ← ↓ ← ↓ ← ← ↑ → ↓ → ↑ /
→ ↑ → ↑ ↑ ← ← ↓ /
← ↓ ↓ ↓ → ↑ /
→ ↑ → ↑ ↑ ← ← ↓ /
↑ → → ↓ ↓ ← ↓ ← ↓ ← ↑ ↑ ↓ ↓ ← ← ← ↑ ↑ ↑ → → /

↑ ↑ ← /
→ ↑ ↑ ← ← ↓ /
↑ → → ↓ ↓ ↓ ↓ ← ↑ → ↑ ← /
↓ ↓ ← ↑ /
→ → ↑ ↑ ↑ ← ← ↓ /
↑ → → ↓ ↓ ↓ ← ← ↓ ← ↑ /

← ← ← ↑ ↑ → /
← ↓ ↓ → → ↑ /
→ ↑ ↑ ↑ ← ↓ /
← ← ↓ ↓ ↓ → ↑ ← ↑ → /
↓ → ↓ → ↑ /

← ← ← ↑ → → ← ← ↑ ↑ → → ↓ ↑ ← ← ↓ ↓ ↓ → → → → ↑ ↑ ← ↑ ← ↓ /
→ → ↓ ← /
↓ ← ← ← ↑ → /
↓ → → ↑ ↑ ← ↑ → /

← ← ← ↓ ← ↑ ↑ ↑ → ↓ ← ↓ → ↑ ↑ → → ↓ → ↓ ← /
→ ↓ ↓ ← ↑ → ↑ ← /
↑ ↑ ← ← ← ↓ ↓ → /
↑ ↑ → → ↓ → ↓ ← /
↑ ↑ ← ← ← ↓ ↓ → /
↑ ↑ → → ↓ ↓ ↓ → ↓ ← ← /

↓ ↓ ← ↑ /
← ← ↓ ← ↑ → → → → ↑ ↑ ↑ ← ↓ /
← ← ↑ ← ↓ /
→ → → → ↓ ↓ ← ← ← ↓ ← ↑ /
→ → → → ↑ ↑ ← ← ← ↑ ← ↓ /
→ ↓ ↑ → → → ↓ ↓ ← ← ← /

↑ ↑ → ↓ /
→ → ↑ → ↓ ↓ ↓ ← → ↑ ↑ ← ↓ → ↓ ← /
↑ ↑ ← ← ← ↓ ↓ ↓ → ↑ /
← ↑ ↑ ↑ → ↓ /
← ↓ ↓ → /
← ↑ ↑ → → → → ↓ ↓ ← /
↑ ↑ ← ← ← ↓ ↓ ↓ → ↑ /
← ↑ ↑ → → → ↑ → ↓ ↓ ↓ /

↑ → ↑ ← /
↓ ↓ ← ← ← ↑ ↑ → /
← ↓ ↓ → → → ↑ ↑ ↑ → ↑ ← ← ← ↓ ↑ ← ↓ ↓ → /
↑ ↑ → → → ↓ ↓ ← /
↑ ↑ ← ← ← ↓ ↓ → /
↑ ↑ → → ↓ ↓ → ↓ ← /
↓ ← ← ← ↑ ← ↑ → → /
← ↓ ↓ → → → → ↑ ↑ ← /
↓ ↓ ← ← ← ↑ ↑ → /
← ↓ ↓ → → → → ↑ ↑ ← /
↓ ↓ ← ← ← ↑ ↑ → /
← ↓ ↓ → → → ↑ ↑ ↑ → ↑ ← ← ← ← /