:root {
    --bg: #0f172a;
    --card: #1e293b;
    --accent: #3b82f6;
    --text: #f1f5f9;
    --text-dim: #94a3b8;
    --border: #334155;
    --radius: 4px;
    --color-beginner: #10b981; --color-basic: #3b82f6; --color-intermediate: #f59e0b; --color-advanced: #8b5cf6; --color-competition: #ef4444;
    --base-font-size: 14px;
    
    --font-size-xs: 0.714rem;
    --font-size-sm: 0.857rem;
    --font-size-base: 1rem;
    --font-size-md: 1.071rem;
    --font-size-lg: 1.214rem;
}

@media (max-width: 480px) {
    :root {
        --base-font-size: 12px;
    }
}

@media (min-width: 481px) and (max-width: 768px) {
    :root {
        --base-font-size: 13px;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    :root {
        --base-font-size: 14px;
    }
}

@media (min-width: 1025px) {
    :root {
        --base-font-size: 15px;
    }
}

* { box-sizing: border-box; }
body {
    margin: 0; padding: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg); color: var(--text);
    height: 100vh; display: flex; flex-direction: column; overflow: hidden;
    font-size: var(--font-size-sm);
}

#globalLoading { 
    position: fixed; 
    inset: 0; 
    background: #0f172a; 
    z-index: 3000; 
    display: flex; 
    flex-direction: column; 
    align-items: center; 
    justify-content: center; 
}
.spinner { width: 2.143rem; height: 2.143rem; border: 0.214rem solid rgba(255,255,255,0.1); border-left-color: var(--accent); border-radius: 50%; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

.top-nav {
    display: flex; justify-content: space-between; align-items: center;
    padding: 0.714rem 1.143rem; background: var(--card); border-bottom: 1px solid var(--border);
}
.top-nav h1 { font-size: var(--font-size-md); margin: 0; }

.selector-area { background: var(--card); padding: 0.571rem 0.857rem; border-bottom: 1px solid var(--border); }
.selector-row { display: flex; align-items: center; gap: 0.571rem; }
.btn-cat-trigger {
    flex: 1; background: rgba(255,255,255,0.03); border: 1px solid var(--border);
    color: var(--text); padding: 0.714rem 0.857rem; border-radius: var(--radius);
    display: flex; justify-content: space-between; align-items: center; cursor: pointer;
}
.random-btn {
    background: var(--color-competition); color: white; padding: 0.714rem 1rem;
    border-radius: var(--radius); font-size: var(--font-size-sm); font-weight: 600; cursor: pointer;
    white-space: nowrap; transition: opacity 0.3s ease;
}
.random-btn.cooldown { opacity: 0.6; pointer-events: none; }

.diff-bar { display: flex; gap: 0.429rem; overflow-x: auto; padding: 0.571rem 0.857rem; background: var(--bg); scrollbar-width: none; }
.diff-bar::-webkit-scrollbar { display: none; }
.tag-item {
    padding: 0.357rem 0.857rem; border-radius: var(--radius); 
    background: var(--card); border: 1px solid var(--border);
    font-size: var(--font-size-sm); white-space: nowrap; cursor: pointer;
}
.tag-item.active { background: var(--accent); color: white; border-color: var(--accent); }

.content-wrap { flex: 1; display: flex; flex-direction: column; overflow: hidden; }

.mode-switch { display: flex; padding: 0.571rem 0.857rem; gap: 0.571rem; }
.mode-btn {
    flex: 1; padding: 0.571rem; border: 1px solid var(--border); background: var(--card);
    color: var(--text-dim); border-radius: var(--radius); font-size: var(--font-size-sm); cursor: pointer;
}
.mode-btn.active { border-color: var(--accent); color: var(--accent); background: rgba(59, 130, 246, 0.1); }

.list-view { flex: 1; overflow-y: auto; padding: 0 0.857rem 1.429rem; }
.list-item {
    background: var(--card); border-radius: var(--radius); margin-bottom: 0.429rem;
    padding: 0.857rem; border: 1px solid var(--border);
    display: flex; align-items: center; gap: 0.714rem; cursor: pointer;
}
.status-dot { width: 0.429rem; height: 0.429rem; border-radius: 0.143rem; flex-shrink: 0; }
.item-title { font-size: var(--font-size-sm); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

.single-view { display: none; flex-direction: column; flex: 1; overflow: hidden; }
.q-header { display: flex; align-items: center; gap: 0.857rem; padding: 0.857rem 1.143rem; background: var(--card); border-bottom: 1px solid var(--border); font-size: var(--font-size-base); }

.q-body { 
    flex: 1; overflow-y: auto; padding: 1.143rem; 
    scroll-behavior: smooth; 
}
.q-step { 
    padding: 0.857rem; border: 1px solid var(--border); border-radius: var(--radius); 
    margin-bottom: 0.857rem; background: rgba(255,255,255,0.02); line-height: 1.6;
    display: none; 
}

.step-actions {
    padding: 0 1.143rem 0.857rem;
    display: flex; gap: 0.714rem;
}
.step-btn {
    flex: 1; padding: 0.714rem; border-radius: var(--radius);
    font-size: var(--font-size-sm); font-weight: 600; cursor: pointer;
    background: rgba(59, 130, 246, 0.1); border: 1px solid var(--accent); color: var(--accent);
    transition: all 0.2s;
}
.step-btn:active { background: var(--accent); color: white; }

.q-footer {
    padding: 0.857rem 1.143rem; background: var(--card); border-top: 1px solid var(--border);
    display: flex; justify-content: space-between; align-items: center; gap: 0.714rem;
}
.nav-btn {
    flex: 1; padding: 0.714rem; background: var(--accent); border: none; 
    border-radius: var(--radius); color: white; font-weight: 600; 
    cursor: pointer; font-size: var(--font-size-sm);
}
.nav-btn:disabled { background: var(--border); color: var(--text-dim); cursor: not-allowed; }

#randomToast {
    position: fixed; bottom: 8.571rem; left: 50%; transform: translateX(-50%); z-index: 2500;
    display: none; opacity: 0; background: rgba(16, 185, 129, 0.9); color: white;
    padding: 0.714rem 1.429rem; border-radius: 1.429rem; font-size: var(--font-size-sm); text-align: center;
    min-width: 7.143rem; box-shadow: 0 0.286rem 0.857rem rgba(0,0,0,0.3); transition: opacity 0.6s ease, transform 0.6s ease;
}
#randomToast.show { display: block; opacity: 1; transform: translateX(-50%) translateY(0); }
#randomToast.hide { opacity: 0; transform: translateX(-50%) translateY(20px); }

.cat-overlay { position: fixed; inset: 0; background: rgba(15, 23, 42, 0.98); z-index: 2000; display: none; flex-direction: column; }
.cat-overlay.active { display: flex; }
.cat-header { padding: 1rem 1.143rem; border-bottom: 1px solid var(--border); display: flex; justify-content: space-between; align-items: center; }
.cat-content { flex: 1; display: flex; overflow: hidden; }
.main-cats { width: 6.429rem; background: rgba(0,0,0,0.2); border-right: 1px solid var(--border); overflow-y: auto; }
.m-item { padding: 1.143rem 0.714rem; font-size: var(--font-size-sm); text-align: center; color: var(--text-dim); cursor: pointer; }
.m-item.active { color: var(--accent); background: rgba(59, 130, 246, 0.1); font-weight: bold; }
.sub-cats { flex: 1; overflow-y: auto; }
.s-item { padding: 1rem 1.143rem; border-bottom: 1px solid var(--border); font-size: var(--font-size-sm); display: flex; justify-content: space-between; }

.overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.85); backdrop-filter: blur(4px); z-index: 1000; display: none; align-items: center; justify-content: center; padding: 1.429rem; }
.overlay.active { display: flex; }
.overlay-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); width: 100%; max-width: 35.714rem; max-height: 80vh; display: flex; flex-direction: column; }
.ov-header { padding: 1rem; border-bottom: 1px solid var(--border); font-size: 1rem; }
.ov-body { padding: 1rem; overflow-y: auto; flex: 1; }
.ov-close { padding: 0.857rem; text-align: center; color: var(--accent); border-top: 1px solid var(--border); cursor: pointer; }

.dot-beginner { background: var(--color-beginner); } 
.dot-basic { background: var(--color-basic); } 
.dot-intermediate { background: var(--color-intermediate); } 
.dot-advanced { background: var(--color-advanced); } 
.dot-competition { background: var(--color-competition); }