Build a CR-balanced 5e encounter with terrain and tactics that matter

You are a senior D&D 5e dungeon master and encounter designer who builds fights that are memorable because of WHERE and HOW they happen, not just what's on the stat blocks.

Design a single balanced 5e encounter where the terrain and enemy tactics are the point — a fight that feels different because the battlefield and monster behavior create real choices, not a flat slugfest in a 30-foot room.

Party:
- Size and levels: [e.g. '4 PCs, level 5']
- Composition: [e.g. 'fighter, rogue, cleric, wizard — melee-light']
- Resources right now: [FULL / BLOODIED / ONE SHORT REST LEFT / NEAR SPENT]
- Known weaknesses to pressure or avoid: [e.g. 'low WIS saves, no ranged' / 'none — keep it fair']

Environment:
- Location: [e.g. 'rotting rope bridge over a gorge' / 'flooded crypt' / 'crowded market at noon' / 'YOU CHOOSE']
- Hazards or features available: [DESCRIBE, OR 'DESIGN 2-3 THAT MATTER']

Build:
1. The encounter math — the monsters (with CR and source book or MM entry), total adjusted XP, and the difficulty label (Easy/Medium/Hard/Deadly) per the 5e encounter-building rules for my party size. Show the budget math so I can sanity-check it.
2. Why this is balanced for MY party specifically — note if melee-light, AoE-heavy, or save-weak composition shifts the real difficulty off the raw CR, and adjust.
3. The battlefield — a short prose sketch of the terrain, then 2-3 tactical features (cover, elevation, hazards, chokes, interactables) that reward positioning. Each feature should be usable by both sides.
4. Monster tactics — how these specific enemies fight HERE: what they open with, how they use the terrain, when they retreat or call reinforcements, and one clever trick that will surprise seasoned players without being unfair.
5. Win and fail conditions beyond 'reduce to 0 HP' — an objective, a timer, an escape, or a thing the party must protect, so the fight has stakes and a shape.
6. Scaling knob — one sentence on how to dial this up or down on the fly if I misread my party's strength.

Rules:
- Use official 5e stat blocks and the encounter-building XP rules. State whether you are using 2014 or 2024 rules. Do not invent homebrew monsters unless I ask.
- Terrain features must follow 5e rules (cover, difficult terrain, fall damage) so rulings are clean at the table.
- A 'Hard' fight should be genuinely threatening, not a speed bump. Say honestly if my resource level makes a nominally Medium fight Deadly.
- Do not hand the monsters abilities they don't have.

Output: the math, party-specific balance note, battlefield sketch plus features, monster tactics, win/fail conditions, scaling knob.

Success signal: the output is good only if the XP math is shown and correct for my party size, the terrain creates real tactical choices for both sides, and the difficulty accounts for my party's actual composition and resources — not just raw CR.