Clash Royale
Three-minute matches designed for exactly this context. You can complete five competitive matches in a bus ride, make meaningful ladder progress, and the game requires no audio to play competently — visual information is complete. The ranked ladder creates long-term engagement across hundreds of sessions, and the card collection system gives you something to optimize between matches.
Minecraft Pocket Edition
The mobile version carries all core gameplay of the PC version in a format optimized for touch controls. Creative mode in particular is ideal for travel: no pressure, no session length requirements, no failure state. Build something for twenty minutes, save, continue. One of the most genuinely portable versions of a major PC game available.
Final Fantasy XIV (Steam Deck/Handheld)
On a Steam Deck, FFXIV becomes a genuinely excellent travel game. The duty system — queued combat encounters with loading screen buffers — fits naturally around transit interruptions. Gathering and crafting are low-attention activities well-suited to background play on a train.