Replace basic arch

Author: jhinpan

README.md

@@ -116,23 +116,53 @@ APRIL not only improves training efficiency but also achieves:
 
 ### System Design
 
-```
-┌─────────────────────────────────────────────────────┐
-│                   Training Pipeline                  │
-├─────────────────────────────────────────────────────┤
-│                                                      │
-│  ┌──────────────┐    ┌──────────────┐              │
-│  │   Rollout    │───▶│    Buffer    │              │
-│  │   Engine     │    │  Management  │              │
-│  │  (SGLang)    │    └──────────────┘              │
-│  └──────────────┘           │                       │
-│         ▲                   ▼                       │
-│         │            ┌──────────────┐              │
-│         │            │   Training   │              │
-│         └────────────│    Engine    │              │
-│                     │ (Megatron/FSDP)│              │
-│                     └──────────────┘               │
-└─────────────────────────────────────────────────────┘
+```mermaid
+graph TB
+    subgraph Pipeline["🎯 APRIL Training Pipeline"]
+        subgraph Rollout["📊 Rollout Phase"]
+            R1[("🎲 Over-provision<br/>N' > N requests")]
+            R2[("⚡ SGLang<br/>Inference Engine")]
+            R3[("🛑 Active<br/>Interruption")]
+            R1 --> R2
+            R2 --> R3
+        end
+
+        subgraph Buffer["💾 Buffer Management"]
+            B1[("📦 Partial<br/>Rollouts")]
+            B2[("♻️ Resume<br/>Queue")]
+            B3[("✅ Complete<br/>Samples")]
+            B1 --> B2
+            R3 --> B1
+            R3 --> B3
+        end
+
+        subgraph Training["🧠 Training Phase"]
+            T1[("🔄 Policy<br/>Update")]
+            T2[("📈 Loss<br/>Computation")]
+            T3[("⚙️ Megatron/<br/>FSDP Backend")]
+            B3 --> T2
+            T2 --> T1
+            T1 --> T3
+        end
+
+        B2 -.->|Next Iteration| R1
+        T3 -.->|Updated Model| R2
+    end
+
+    style Pipeline fill:#f9f9ff,stroke:#4a5568,stroke-width:2px
+    style Rollout fill:#e6f7ff,stroke:#1890ff,stroke-width:1px
+    style Buffer fill:#fff7e6,stroke:#fa8c16,stroke-width:1px
+    style Training fill:#f0f5ff,stroke:#597ef7,stroke-width:1px
+
+    style R1 fill:#e6f7ff,stroke:#40a9ff
+    style R2 fill:#e6f7ff,stroke:#40a9ff
+    style R3 fill:#e6f7ff,stroke:#40a9ff
+    style B1 fill:#fff7e6,stroke:#ffa940
+    style B2 fill:#fff7e6,stroke:#ffa940
+    style B3 fill:#fff7e6,stroke:#ffa940
+    style T1 fill:#f0f5ff,stroke:#85a5ff
+    style T2 fill:#f0f5ff,stroke:#85a5ff
+    style T3 fill:#f0f5ff,stroke:#85a5ff
 ```
 
 ### Core Components