Find symbols in order as fast as possible. 5 modifications for different challenge levels: • 🔢 Numbers 1→25 (classic, easiest) • 🔢 Numbers 25→1 (backward — harder) • 🔤 Letters A→Z (same principle, alphabet) • 🔤 Letters Z→A (backward alphabet — harder) • 🔀 1-A-2-B-3-C (Schulte-Gorbov: switching between two sequences in parallel) Color mode adds visual noise for extra challenge. Expands peripheral vision, speeds up information scanning, and trains sustained attention.