*{
    margin:0;
    padding:0;
    box-sizing:border-box;
}

body{
    font-family:'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background:#f0f2f5;
    color:#222;
    overflow:hidden;
    height:100vh;
}

/* === TOP NAVBAR === */
.topbar{
    display:flex;
    align-items:center;
    justify-content:space-between;
    background:#1a1a2e;
    color:white;
    padding:0 24px;
    height:56px;
    position:fixed;
    top:0;
    left:0;
    right:0;
    z-index:1000;
    box-shadow:0 2px 8px rgba(0,0,0,0.15);
}

.topbar .brand{
    font-size:20px;
    font-weight:700;
    letter-spacing:0.5px;
    display:flex;
    align-items:center;
    gap:10px;
}

.topbar .brand span{
    background:linear-gradient(135deg,#4fc3f7,#0288d1);
    -webkit-background-clip:text;
    -webkit-text-fill-color:transparent;
}

.topbar nav{
    display:flex;
    align-items:center;
    gap:6px;
}

.topbar nav a{
    color:#ccc;
    text-decoration:none;
    padding:8px 16px;
    border-radius:6px;
    font-size:14px;
    font-weight:500;
    transition:all 0.2s;
}

.topbar nav a:hover,
.topbar nav a.active{
    background:rgba(255,255,255,0.1);
    color:#fff;
}

.topbar .menu-toggle{
    display:none;
    background:none;
    border:none;
    color:white;
    font-size:22px;
    cursor:pointer;
    padding:8px;
}

/* === LAYOUT === */
.layout{
    display:flex;
    margin-top:56px;
    height:calc(100vh - 56px);
}

/* === SIDEBAR TREE === */
.sidebar{
    width:260px;
    background:#fff;
    border-right:1px solid #e0e0e0;
    padding:20px 0;
    overflow-y:auto;
    flex-shrink:0;
    transition:transform 0.3s;
}

.sidebar .tree-section{
    margin-bottom:8px;
}

.sidebar .tree-title{
    display:flex;
    align-items:center;
    gap:8px;
    padding:10px 20px;
    font-size:12px;
    font-weight:700;
    text-transform:uppercase;
    letter-spacing:1px;
    color:#888;
    cursor:pointer;
    user-select:none;
}

.sidebar .tree-title:hover{
    color:#1a1a2e;
}

.sidebar .tree-title::before{
    content:'▶';
    font-size:9px;
    transition:transform 0.2s;
}

.sidebar .tree-section.open .tree-title::before{
    transform:rotate(90deg);
}

.sidebar .tree-links{
    display:none;
    padding:0;
}

.sidebar .tree-section.open .tree-links{
    display:block;
}

.sidebar .tree-links a{
    display:flex;
    align-items:center;
    gap:10px;
    padding:9px 20px 9px 36px;
    color:#444;
    text-decoration:none;
    font-size:14px;
    border-left:3px solid transparent;
    transition:all 0.2s;
}

.sidebar .tree-links a::before{
    content:'';
    width:6px;
    height:6px;
    border-radius:50%;
    background:#ccc;
    flex-shrink:0;
    transition:background 0.2s;
}

.sidebar .tree-links a:hover{
    background:#f0f7ff;
    border-left-color:#0288d1;
    color:#0288d1;
}

.sidebar .tree-links a:hover::before{
    background:#0288d1;
}

.sidebar .tree-links a.active{
    background:#e3f2fd;
    border-left-color:#0288d1;
    color:#0288d1;
    font-weight:600;
}

.sidebar .tree-links a.active::before{
    background:#0288d1;
}

/* === CONTENT AREA === */
.content{
    flex:1;
    padding:30px 40px;
    overflow-y:auto;
    background:#f0f2f5;
}

.tool-container{
    max-width:900px;
    margin:0 auto;
}

.tool-container h1{
    font-size:24px;
    color:#1a1a2e;
    margin-bottom:6px;
}

.tool-container .tool-desc{
    color:#666;
    font-size:14px;
    margin-bottom:24px;
}

/* === FORM ELEMENTS === */
textarea{
    width:100%;
    min-height:250px;
    padding:16px;
    border:2px solid #e0e0e0;
    border-radius:10px;
    font-size:14px;
    font-family:'Courier New', monospace;
    background:#fff;
    resize:vertical;
    transition:border-color 0.2s;
}

textarea:focus{
    outline:none;
    border-color:#0288d1;
}

.buttons{
    margin-top:16px;
    display:flex;
    gap:10px;
    flex-wrap:wrap;
}

button{
    background:linear-gradient(135deg,#0288d1,#0277bd);
    color:white;
    border:none;
    padding:11px 22px;
    border-radius:8px;
    cursor:pointer;
    font-size:14px;
    font-weight:600;
    transition:all 0.2s;
    box-shadow:0 2px 6px rgba(2,136,209,0.3);
}

button:hover{
    transform:translateY(-1px);
    box-shadow:0 4px 12px rgba(2,136,209,0.4);
}

button:active{
    transform:translateY(0);
}

button.secondary{
    background:#fff;
    color:#444;
    border:2px solid #e0e0e0;
    box-shadow:none;
}

button.secondary:hover{
    border-color:#0288d1;
    color:#0288d1;
    box-shadow:none;
}

.output{
    margin-top:20px;
    background:#fff;
    border:2px solid #e0e0e0;
    border-radius:10px;
    padding:20px;
    white-space:pre-wrap;
    font-family:'Courier New', monospace;
    font-size:14px;
    overflow:auto;
    max-height:400px;
    min-height:60px;
}

/* === TOOL GRID (Homepage) === */
.tool-grid{
    display:grid;
    grid-template-columns:repeat(auto-fill,minmax(280px,1fr));
    gap:20px;
    margin-top:24px;
}

.tool-card{
     background:white;
     border-radius:12px;
     padding:24px;
     border:1px solid #e0e0e0;
     transition:all 0.2s;
     position:relative;
     overflow:visible;
     pointer-events:auto;
 }

 .tool-card::before{
     content:'';
     position:absolute;
     top:0;
     left:0;
     right:0;
     height:4px;
     background:linear-gradient(135deg,#4fc3f7,#0288d1);
     opacity:0;
     transition:opacity 0.2s;
     pointer-events:none;
 }

.tool-card:hover{
    transform:translateY(-3px);
    box-shadow:0 8px 24px rgba(0,0,0,0.08);
}

.tool-card:hover::before{
    opacity:1;
}

.tool-card .card-icon{
    width:42px;
    height:42px;
    border-radius:10px;
    background:linear-gradient(135deg,#e3f2fd,#bbdefb);
    display:flex;
    align-items:center;
    justify-content:center;
    font-size:20px;
    margin-bottom:14px;
}

.tool-card h2{
    font-size:17px;
    color:#1a1a2e;
    margin-bottom:8px;
}

.tool-card p{
    color:#666;
    font-size:13px;
    line-height:1.5;
    margin-bottom:16px;
}

.tool-card a.card-btn{
     display:inline-flex;
     align-items:center;
     gap:6px;
     text-decoration:none;
     color:#0288d1;
     font-size:14px;
     font-weight:600;
     transition:gap 0.2s;
     cursor:pointer;
     pointer-events:auto;
     position:relative;
     z-index:10;
 }

 .tool-card a.card-btn:hover{
     gap:10px;
 }

 .tool-card a.card-btn::after{
     content:'→';
 }

/* === FOOTER === */
.footer{
    display:none;
}

/* === ERROR MESSAGE === */
.error-msg{
    color:#d32f2f;
    background:#ffebee;
    border:1px solid #ffcdd2;
    border-radius:8px;
    padding:12px 16px;
    margin-top:16px;
    font-size:14px;
    display:none;
}

.error-msg.show{
    display:block;
}

/* === RESPONSIVE === */
@media(max-width:900px){
    .topbar .menu-toggle{
        display:block;
    }

    .sidebar{
        position:fixed;
        top:56px;
        left:0;
        bottom:0;
        z-index:999;
        transform:translateX(-100%);
        box-shadow:4px 0 16px rgba(0,0,0,0.1);
    }

    .sidebar.open{
        transform:translateX(0);
    }

    .content{
        padding:20px 16px;
    }
}

@media(max-width:600px){
    .topbar nav{
        display:none;
    }

    .tool-grid{
        grid-template-columns:1fr;
    }
}