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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    background: #f5f5f5;
    color: #333;
}

.essay-checker-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 15px;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 5px;
    margin-bottom: 20px;
    border-bottom: 2px solid #ddd;
    flex-wrap: wrap;
}

.tab-btn {
    padding: 12px 16px;
    background: none;
    border: none;
    border-bottom: 3px solid transparent;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    color: #666;
    transition: all 0.3s;
    white-space: nowrap;
}

.tab-btn.active {
    color: #0073aa;
    border-bottom-color: #0073aa;
}

.tab-btn:hover {
    color: #0073aa;
}

/* Tab Content */
.tab-content {
    display: none;
    animation: fadeIn 0.3s;
}

.tab-content.active {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
}

.tab-content > div {
    flex: 1 1 auto;
    min-width: 0;
    max-width: 100%;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* Form Fields */
.form-group {
    margin-bottom: 16px;
}

label {
    display: block;
    margin-bottom: 6px;
    font-weight: 500;
    font-size: 14px;
}

input[type="text"],
input[type="password"],
textarea,
select {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-size: 14px;
    font-family: inherit;
    transition: border-color 0.3s;
}

input[type="text"]:focus,
input[type="password"]:focus,
textarea:focus,
select:focus {
    outline: none;
    border-color: #0073aa;
    box-shadow: 0 0 0 3px rgba(0, 115, 170, 0.1);
}

textarea {
    min-height: 120px;
    resize: vertical;
}

/* API Key Grid */
.api-keys-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
}

@media (min-width: 768px) {
    .api-keys-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (min-width: 1024px) {
    .api-keys-grid {
        grid-template-columns: 1fr 1fr 1fr;
    }
}

/* Buttons */
.button-group {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-top: 20px;
}

button {
    flex: 1;
    min-width: 120px;
    padding: 12px 16px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s;
}

#check-btn {
    background: #0073aa;
    color: white;
}

#check-btn:hover:not(:disabled) {
    background: #005a87;
    transform: translateY(-2px);
    box-shadow: 0 2px 8px rgba(0, 115, 170, 0.3);
}

#check-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

/* Results */
#result {
    background: white;
    border: 1px solid #ddd;
    border-radius: 4px;
    padding: 16px;
    margin-top: 20px;
    line-height: 1.6;
    word-wrap: break-word;
    overflow-x: auto;
}

#result:empty {
    display: none;
}

#result br {
    display: block;
    content: "";
    margin: 8px 0;
}

/* Color Tags */
span[style*="color:#d32f2f"],
span[style*="color:#f57c00"],
span[style*="color:#388e3c"],
span[style*="color:#0073aa"] {
    padding: 2px 6px;
    border-radius: 3px;
    display: inline-block;
    margin: 2px 0;
}

/* Image Preview */
.image-preview {
    max-width: 100%;
    max-height: 300px;
    margin-top: 10px;
    border-radius: 4px;
    border: 1px solid #ddd;
}

#image-preview-container {
    margin-top: 10px;
}

/* Loading State */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(0, 115, 170, 0.3);
    border-radius: 50%;
    border-top-color: #0073aa;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Error Messages */
.error-message {
    background: #fee;
    color: #c33;
    padding: 12px;
    border-radius: 4px;
    margin-top: 10px;
    border-left: 4px solid #c33;
}

.success-message {
    background: #efe;
    color: #3c3;
    padding: 12px;
    border-radius: 4px;
    margin-top: 10px;
    border-left: 4px solid #3c3;
}

/* Mobile Optimizations */
@media (max-width: 640px) {
    .essay-checker-container {
        padding: 10px;
    }

    /* Stack tab content vertically on mobile */
    .tab-content.active {
        flex-direction: column;
        gap: 15px;
    }

    .tab-content > div {
        width: 100%;
    }

    .tabs {
        gap: 2px;
        margin-bottom: 15px;
    }

    .tab-btn {
        padding: 10px 12px;
        font-size: 12px;
        flex: 1;
        text-align: center;
    }

    label {
        font-size: 13px;
        margin-bottom: 5px;
    }

    input[type="text"],
    input[type="password"],
    textarea,
    select {
        font-size: 16px; /* Prevents zoom on iOS */
        padding: 12px;
    }

    textarea {
        min-height: 100px;
    }

    .button-group {
        gap: 8px;
        margin-top: 15px;
    }

    button {
        min-width: 100px;
        padding: 11px 14px;
        font-size: 13px;
    }

    #result {
        padding: 12px;
        margin-top: 15px;
        font-size: 13px;
    }

    .image-preview {
        max-height: 250px;
    }

    .api-keys-grid {
        grid-template-columns: 1fr;
    }
}

/* Tablet Optimizations */
@media (min-width: 641px) and (max-width: 1024px) {
    .essay-checker-container {
        padding: 12px;
    }

    .api-keys-grid {
        grid-template-columns: 1fr 1fr;
    }
}

/* Desktop Optimizations */
@media (min-width: 1025px) {
    .essay-checker-container {
        padding: 20px;
    }

    .api-keys-grid {
        grid-template-columns: 1fr 1fr 1fr;
    }

    #result {
        padding: 20px;
        font-size: 14px;
    }

    /* Ensure 2-column layout on desktop with max 50% width each */
    .tab-content.active {
        display: flex;
        gap: 20px;
    }

    .tab-content > div {
        flex: 0 1 calc(50% - 10px);
        max-width: calc(50% - 10px);
    }
}